Slow release of fragrant compounds in perfumery using alpha-keto esters

ABSTRACT

The present invention describes a fragrance delivery system which releases fragrant aldehydes or ketones and/or fragrant compounds containing an olefin function upon exposure to light. This system comprises α-keto esters of formula  
                 
 
     in which R′* and R″* have the meaning as defined in the application and which are generally, in case of R′*, an alkyl group carrying an abstractable hydrogen in γ-position relative to the α-keto function and carrying a moiety from which is derived a fragrant compound containing an olefin function, and, in case of R″*, the organic part of a primary or secondary alcohol from R″*OH which is derived a fragrant aldehyde or ketone.

BRIEF SUMMARY OF THE INVENTION

[0001] The present invention describes a fragrance delivery system whichreleases fragrant aldehydes or ketones and/or fragrant compoundscontaining an olefin function upon exposure to light. This systemcomprises α-keto esters of formula

[0002] in which R′* and R″* have the meaning as defined in theapplication and which are generally, in case of R′*, an alkyl groupcarrying an abstractable hydrogen in γ-position relative to the α-ketofunction and carrying a moiety from which is derived a fragrant compoundcontaining an olefin function, and, in case of R″*, the organic part ofa primary or secondary alcohol from R″*OH which is derived a fragrantaldehyde or ketone.

BACKGROUND OF THE INVENTION

[0003] The present invention relates to the field of perfumery. Itrelates, more particularly, to α-keto esters, as defined below, ofalcohols which are precursors of fragrant aldehydes and ketones andwhich are capable of releasing said fragrant ketone or aldehyde uponexposure to light, more particularly daylight. Said α-keto esters mayfurthermore contain, in α-position to the keto group, an alkyl groupwhich may contain various substituents and which alkyl group is derivedfrom a fragrant molecule possessing an olefinic unsaturation. Theunsaturated molecule and/or the aldehyde or ketone are released uponexposure to light, in particular daylight, of the α-keto ester.

[0004] There exists, in perfumery, a particular interest in compoundswhich are capable of “fixing” fragrant molecules, for example bychemical bonding or intramolecular forces like absorption, and releasingsaid fragrant molecules over a prolonged period of time, for example bythe action of heat, enzymes, or even sunlight. Fragrant molecules haveto be volatile in order to be perceived. Although many fragrantcompounds are known which show a good substantivity, i.e. they willremain on a surface to which they have been applied for several days andcan hence be perceived over such a period of time, a great number offragrant compounds are very volatile, and their characteristic smell canno longer be perceived several hours after their application.

[0005] It is thus desirable to dispose of fragrance delivery systemswhich are capable of releasing the fragrant compound or compounds in acontrolled manner, maintaining a desired smell over a prolonged periodof time.

DETAILED DESCRIPTION OF THE INVENTION

[0006] We have now developed a fragrance delivery system which iscapable of releasing fragrant aldehydes or ketones and/or fragrantcompounds containing an olefin function upon exposure to light, and inparticular daylight.

[0007] The object of the present invention is a fragrance deliverysystem comprising α-keto esters of formula

[0008] in which

[0009] R′* is hydrogen or a linear or branched, unsubstituted orsubstituted alkyl group or alkylene group from C₁ to C₃₅, anunsubstituted or substituted cycloalkyl group from C₃ to C₈, anunsubstituted or substituted phenyl group, wherein said alkyl, alkylene,cycloalkyl and phenyl groups may comprise one or several hetero atomsnot directly linked to the α-keto group and selected from the groupconsisting of oxygen, nitrogen, phosphorous and sulfur, or

[0010] R′* is a substituted or unsubstituted, linear or branched alkylgroup carrying an abstractable hydrogen in γ-position relative to theα-keto function and comprising a moiety from which is derived a fragrantcompound containing an olefin function, such that said fragrant compoundcontaining an olefin function is eliminated after abstraction of saidγ-hydrogen atom;

[0011] R″* is hydrogen or a methyl, ethyl or tert-butyl group or is theorganic part of a primary or secondary alcohol from which is derived afragrant aldehyde or ketone, and at least one of the groups R′* and R″*being a group which is derived from a fragrant compound.

[0012] In the above definition, when reference is made to a fragrantcompound, aldehyde or ketone, it is always meant a compound which notonly has an odor, but which is also known to a person skilled in the artas being useful as a perfuming ingredient for the formulation ofperfumes or perfumed articles. The criteria a useful perfumingingredient has to fulfil are known to a person skilled in the art andinclude, amongst others, a certain originality of the odoriferous note,stability and a certain price/performance ratio. Non-limiting examplesfor fragrant compounds which can be used with the α-keto esters of theinvention will be mentioned below.

[0013] The α-keto esters of the above formula (I) release fragrantcompounds upon exposure to light, in particular daylight. The α-ketoesters of formula (I), however, are also capable of releasing a fragrantcompound containing an olefin function from the group R′* in 1-positionrelative to the keto function, or a fragrant aldehyde or ketone which isderived from the alcohol R″*OH from which the organic part R″* ispresent in the ester function of the keto esters of the presentinvention, or even both.

[0014] From the above, it is clear that when reference is made to theorganic part R″* of a fragrant alcohol R″*OH, R″* is the hydrocarbylrest of said alcohol, e.g. a menthyl radical in case R″*OH is menthol.

[0015] The release of the fragrant compound from the keto esters occursin an elimination reaction after an intramolecular transfer of anabstractable hydrogen radical, in γ-position to the α-keto function, tosaid keto function. The respective part of the molecule from which thehydrogen radical has been abstracted is subsequently released from thereduced keto ester, with concomitant formation of a double bond. Theabove is illustrated in the scheme below in which possible substituentsin the respective parts of the molecules have been omitted for reasonsof clarity. The double bonds which will be formed after elimination areindicated by dotted lines.

[0016] It is to be understood that the α-keto esters of the presentinvention can release only one or both molecules of fragrant compoundper molecule of α-keto ester. When the hydrogen transfer to the α-ketofunction is able to occur from the one or the other side of saidfunction, as illustrated above, a certain part of the molecules willrelease a ketone or aldehyde and a certain part will release the olefincompound. The proportions of the two products released depend on therelative rate of each hydrogen transfer reaction. According to theeffect desired, the α-keto esters of the invention can be tailored torelease exclusively a fragrant ketone or aldehyde, or exclusively afragrant compound containing an olefin group, or both. When only one ofthe two classes of fragrant compounds is to be released from the α-ketoesters of the invention, the part of the molecule from which no releaseshall occur does not contain an abstractable hydrogen atom in γ-positionto the keto function, i.e. either no hydrogen atom at all is present inthe said position, or it is one which is not abstracted.

[0017] It is also clear that the α-keto esters according to theinvention can, in a first step, release the olefin compound underformation of a molecule which does not any longer contain anabstractable hydrogen atom in γ-position to the keto function (left sideof the molecule as designed above) ; in a second step, this molecule canthen release the ketone or aldehyde from the ester function.

[0018] A fragrance delivery system which contains the α-keto esters ofthe above formula (I) has the advantages that the release of thefragrant compound occurs in a more or less constant amount. No initialburst of very intensive odor which becomes imperceptible after arelatively short period of time occurs, as is often observed withvolatile aldehydes or ketones or fragrant compounds containing an olefingroup. With the α-keto esters of the present invention, suchdisadvantages are obviated because the esters will remain on a surfaceto which they have been applied or in the solution into which they havebeen incorporated. Upon exposure to light, the fragrant compound orcompounds are released, and this reaction can provide perceptibleamounts of the compound over days or weeks, depending, amongst others,on the amount or the concentration of the α-keto esters, the time ofexposure to light and its intensity.

[0019] A further advantage of the a-keto esters according to formula (I)is the protection of the reactive, unstable aldehyde or keto function inthe molecules to be released against degradation which may occur duringstorage.

[0020] Additionally, the α-keto esters of the present invention allowfor the generation of mixtures of two different fragrant compounds, andin different proportions, if desired.

[0021] In principle, any fragrant aldehyde or ketone which is known inthe art can be released from the α-keto esters of the invention in whichthey are chemically bound in the form of the ester of theircorresponding secondary or primary alcohol.

[0022] Non-limiting examples for fragrant aldehydes which can bereleased from the α-keto esters include saturated and unsaturated linearand branched aldehydes from C₆ to C₁₃, citral, citronellal, campholenicaldehyde, cinnamic aldehyde, hexylcinnamic aldehyde, formyl pinane,hydroxycitronellal, cuminic aldehyde, vanillin, ethylvanillin,Lilial®[3-(4-tert-butylphenyl)-2-methylpropanal; origin: Givaudan-RoureSA, Vernier, Switzerland], Lyral® [4- and3-(4-hydroxy-4-methylpentyl)-3-cyclohexene-1-carbaldehyde; origin:International Flavors and Fragrances, USA], Bourgeonal®[3-(4-tert-butylphenyl)propanal; origin: Quest International, Naarden,Netherlands], heliopropanal [3-(1,3-benzodioxol-5-yl)-2-methylpropanal;origin: Firmenich SA, Geneva, Switzerland], Zestover(2,4-dimethyl-3-cyclohexene-1-carbaldehyde; origin: Firmenich SA,Geneva, Switzerland), Trifernal® (3-phenylbutanal ; origin: FirmenichSA, Geneva, Switzerland), α-sinensal, (4-methylphenoxy)acetaldehyde,1,3-benzodioxol-5-carboxaldehyde (heliotropine), Scentenal®[8(9)-methoxy-tricyclo[5.2.1.0.(2,6)]decane-3-(4)-carbaldehyde; origin:Firmenich SA, Geneva, Switzerland], Liminal®[(4R)-1-p-menthene-9-carbaldehyde; origin: Firnenich SA, Geneva,Switzerland], Cyclosal [3-(4-isopropylphenyl)-2-methylpropanal; origin:Firnenich SA, Geneva, Switzerland], ortho- and para-anisaldehyde,3-methyl-5-phenylpentanal, Acropal®[4-(4-methyl-3-pentenyl)-3-cyclohexene-1-carbaldehyde; origin:Givaudan-Roure SA., Vernier, Switzerland], Intreleven® aldehyde (mixtureof 10-undecenal and 9-undecenal; origin: International Flavors &Fragrances, USA), muguet aldehyde [(3,7-dimethyl-6-octenyl)acetaldehyde;origin: International Flavors & Fragrances, USA],2,6-dimethyl-5-heptanal, Precyclemone® B[1-methyl-4-(4-methyl-3-pentenyl)-3-cyclohexen-1-carbaldehyde; origin:International Flavors & Fragrances, USA] and Isocyclocitral®(2,4,6-trimethyl-3-cyclohexene-1-carbaldehyde; origin: InternationalFlavors & Fragrances, USA).

[0023] Non-limiting examples for ketones which can be released from theα-keto esters include camphor, carvone, menthone, ionones, irones,damascenones and damacones, benzyl acetone (4-phenyl-2-butanone),1-carvone, 4-(4-hydroxy-1-phenyl)-2-butanone (raspberry ketone),Hedione® (methyl dihydrojasmonate; origin: Firmenich SA, Geneva,Switzerland), Neobutenone[1-(5,5-dimethyl-1-cyclohexen-1-yl)-4-penten-1-one; origin: FirmenichSA, Geneva, Switzerland], Calone®(7-methyl-2H,4H-1,5-benzodioxepin-3-one; origin: C.A.L. SA, Grasse,France), Sulfox [(1R,4R)-8-mercapto-3-p-menthanone; origin: FirmenichSA, Geneva, Switzerland], Orivone®[4-(1,1-dimethylpropyl)-1-cyclohexanone; origin: International Flavors &Fragrances, USA], Delphone (2-pentyl-1-cyclopentanone; origin: FirmenichSA, Geneva, Switzerland), 2-naphthalenyl-1-ethanone, Veloutone(2,2,5-trimethyl-5-pentyl-1-cyclopentanone; origin: Firmenich SA,Geneva, Switzerland), 4-isopropyl-2-cyclohexen-1-one, Iso E Super®[isomer mixture of1-(octahydro-2,3,8,8-tetrame-2-naphthalenyl)-1-ethanone; origin:International Flavors & Fragrances, USA], Plicatone[5-methyl-exo-tricyclo[6.2.1.0(2,7)]undecan-4-one; origin: Firmenich SA,Geneva, Switzerland] ; and macrocyclic ketones such as, for exampleExaltone® (cyclopentadecanone), Delta Muscenone (mixture of3-methyl-4-cyclopentadecen-1-one and 3-methyl-5-cyclopentadecen-1-one)and Muscone (3-methyl-1-cyclopentadecanone), all from Firmenich SA,Geneva, Switzerland.

[0024] With respect to the fragrant compounds carrying an olefin group,in principle any compound containing such olefin group and, in addition,any osmophoric group known in perfumery can be used. As non-limitingexamples for osmophoric groups, one can cite alcohol, ether, ester,aldehyde and keto groups, the thio analogues of the said groups,nitrile, nitro and olefin groups.

[0025] As non-limiting examples for fragrant compounds which carry anolefin group, there can be cited linalool, 1,3,5-undecatrienes, myrcene,myrcenol, dihydromyrcenol, nerolidol, sinensals, limonene, carvone,farnesenes, isopentyrate (1,3-dimethyl-3-butenyl isobutyrate; origin:Firmenich SA, Geneva, Switzerland), allyl 3-methylbutoxyacetate,eugenol, Rosalva (9-decen-1-ol; origin: International Flavors &Fragrances, USA), and allyl heptanoate.

[0026] It is quite obvious, however, that the invention is perfectlygeneral and can relate to many other aldehydes, ketones and olefinswhich are useful as fragrant compounds. The person skilled in the art isquite able to choose these compounds from the general knowledge in theart and from the olfactive effect it is desired to achieve. The abovelist is therefore more illustrative for the compounds which are known toa person skilled in the art, and whose delivery can be improved. It isclearly quite impossible to cite in an exhaustive manner all aldehydes,ketones and olefins which have a pleasant odor and which can be used inthe form of derivatives in the α-keto esters of formula (I) from whichthey are released upon exposure to light.

[0027] The α-keto esters of the present invention are in particularappropriate for delivering fragrant aldehydes, ketones and fragrantcompounds containing an olefin group which are very volatile or whichhave a low perception threshold. Preferred aldehydes and ketones includecitronellal, citral, hydroxycitronellal, Hedione®, Lilial®, raspberryketone, anisaldehyde, menthone, Delphone, Orivone®,2-naphthalenyl-1-ethanone, and aldehydes from C₆ to C₁₃, saturated orunsaturated linear or branched. Preferred fragrant compounds containingan olefin group include linalool, myrcene, myrcenol and Rosalva®.

[0028] In case the α-keto esters of the present invention are used torelease exclusively aldehydes or ketones, the group R′* is hydrogen,phenyl, cyclohexyl or cyclopentyl, methyl, ethyl, n-propyl, isopropyl,sec-butyl, isobutyl or tert-butyl, i.e. groups which do not provide anabstractable hydrogen atom in γ-position to the α-keto function or whichdo not form a stable radical when a hydrogen radical is abstracted fromthem. In the latter case, small amounts of olefin may be formed whichhowever do not interfere with the aldehyde or ketone released.

[0029] Likewise, when the α-keto esters of the present invention areused to release a fragrant compound containing an olefin group only,then the group R″* will be hydrogen or a methyl, ethyl or tert-butylgroup, thus a group which does not provide an abstractable proton inγ-position to the α-keto function or which do not form a stable radicalwhen a hydrogen radical is abstracted from them.

[0030] It is preferred when the fragrance delivery system of the presentinvention contains α-keto esters of formula (I) in which R″* is theorganic part of a primary or secondary alcohol from which is derived afragrant aldehyde or ketone and in which R′* is a phenyl, cyclohexyl orcyclopentyl group or a linear or branched alkyl group from C₁ to C₄.

[0031] A fragrance delivery system containing the α-keto esters offormula (I) may comprise a solvent the choice of which is not supposedto be critical. Suitable classes of solvents include alcohols, ethers,esters, ketones, amines and aminoalcohols.

[0032] Depending on the general application conditions or on the productinto which the α-keto esters according to the present invention areincorporated, one can sometimes also observe the release of alcoholsR″*OH, due to saponification of the ester function, or due to reductionof the aldehyde or ketone formed by irradiation.

[0033] The α-keto esters of formula (I) can be prepared, on the onehand, by esteriication of the respective α-ketoacids with the primary orsecondary alcohols which are the precursors of the fragrant aldehydesand ketones to be releasead. Another way for the preparation of theα-keto esters of the present invention is the reaction of thebis(oxalyl) ester of the primary or secondary precursor alcohol R″*OHwith the Grignard compound of the appropriate group R′* as defined informula (I). The reaction is illustrated in the scheme I below.

[0034] The bis(oxalyl) ester is prepared from oxalyl chloride and thedesired alcohol, see Synth. Commun. 1981, (11), 943-946 and Org. Synth.Coll. Vol. II 1943, 425-427.

[0035] Another synthetic route leading to the desired cc-keto esters offormula (I) is the Grignard reaction of the readily availablebis(oxalyl)esters of lower aliphatic alcohols such as, for example,methanol, ethanol or propanol, with the Grignard compound of therespective group R′*, resulting in the intermediate ester (II). Thissaid ester (II) is then submitted to a transesterification reaction withthe respective precursor alcohol R″*OH, to give the desired α-ketoester. This reaction is outlined in the following scheme II in which R′*and R″* have the meaning defined in formula (I). Hal is Cl, Br or I andR is a lower alkyl group such as, for example, methyl, ethyl, propyl orbutyl.

[0036] Various α-keto esters of formula (I) in which R′* is hydrogen ora phenyl or methyl group and R″* is derived from the alcohol precursorof a fragrant aldehyde are described in the literature.

[0037] Also known is hexyl (cyclohexyl)oxoacetate (see DE-OS 29 09 951to Bayer AG, describing the use of the said compound as starting productfor the synthesis of catalysts for the polymerisation of olefins), whichwould release n-hexanal upon irradiation.

[0038] In Biochem. Z. 1935, (277), p 426-436, there is described thesynthesis of the (-)-bornyl ester of (4-methylphenyl)oxoacetic acid,i.e. (-) (1S,2R), 1,7,7-trimethylbicyclo[2.2.1]heptan-2-yl(4-methylphenyl)oxoacetate. The compound is characterized by itsphysical data.

[0039] There are furthermore known, from the chemical literature,various compounds according to the above formula (I) wherein OR″* is amenthyl or a benzyl group, with the groups R′* being various alkyl,alkenyl, cycloalkyl or phenyl groups as defined above.

[0040] There is nowhere found, however, any description or hintconcerning the value of the compounds according to formula (I) inperfumery as a photosensitive molecule which will release a fragrantcompound upon irradiation.

[0041] In the book of S. Arctander, Perfume and Flavors Chemicals, 1969,Montclair, N.J., USA, there are mentioned decyl 2-oxopropanoate,(Z)-3-hexenyl 2-oxopropanoate and 2-ethyl-3-methylbutyl 2-oxopropanoate,with a short description of their odor and their synthesis. It is notmentioned that the said molecules release fragrant compounds uponirradiation.

[0042] The release of the above-mentioned fragrant compounds from thedelivery system occurs upon the exposure to light, e.g. the normaldaylight which can penetrate through ordinary windows in houses andwhich is not particularly rich in UV-radiation. It goes without sayingthat upon exposure to bright sunlight, in particular outdoors, therelease of the fragrant alcohol, aldehyde, ketone or alkene will occurfaster and to a greater extent than upon exposure to the light in a roominside a building. Of course, the reaction which releases the fragrantcompound from the delivery system can also be initiated by anappropriate artificial lamp.

[0043] The fragrance delivery systems of the present invention can beused in any application in which a prolonged, defined release of theabove-mentioned fragrant compounds is desired. They therefore mostlyfind use in functional perfumery, in articles which are exposed todaylight when in use or which are applied to other articles whichthereafter are exposed to daylight. Suitable examples includeair-fresheners in liquid and solid form which, with the delivery systemof the present invention, still can release a fragrance whenconventional air-fresheners, i.e. those not containing the system of thepresent invention, are exhausted. Other examples are various cleanersfor the cleaning of surfaces of all kinds, e.g. window and householdcleaners, all purpose-cleaners and furniture polish. The surfaces whichhave been cleaned with such cleaners will diffuse the smell of theperfume much longer than when cleaned with conventional cleaners. Otherrepresentative examples include detergents for fabric wash, fabricconditioners and fabric softeners which can also contain the deliverysystem of the present invention and which products can be in the form ofpowders, liquids or tablets. The fabrics and clothes washed or treatedwith such detergents or softeners will diffuse the fragrant compoundeven after having been stored for weeks or even months, in a dark place,like a wardrobe.

[0044] The release of the fragrant compound occurs in all theabove-mentioned application examples. All possible types of window,household, all-purpose cleaners, air-fresheners, detergent, fabric washand fabric softeners can be used with the fragrance delivery system ofthe present invention, which has revealed itself to be useful in alltypes of these above-mentioned application examples.

[0045] In the field of body care, the delivery systems according to thepresent invention have shown themselves to be particularly appropriatefor an application in the hair care area, and specific examples includeshampoos, hair conditioners, in particular leave-in conditioners,hairspray and other hair care products.

[0046] It can be said that generally all products which can be appliedto a surface which is exposable to light may contain the system of thepresent invention. Examples include surfaces which belong to the humanbody, like skin or hair, surfaces in buildings and apartments, likefloors, windows, tiles or furniture, or surfaces of fabrics, e.g.clothes. It is clear that the system of the invention can also be usedto release fragrances from liquids, like in liquid air-fresheners. Thepossible applications of this type, however, appear to be less generalthan the application on the various surfaces mentioned wherein the esterof the invention will be deposed as a film on the respective surface.

[0047] Of course, the above examples are only illustrative andnon-limiting as referring to preferred embodiments. All other currentarticles in functional and fine perfumery may contain the system of thepresent invention, and these articles include soaps, bath or showergels, cosmetic preparations, body deodorants, and even perfumes orcolognes.

[0048] In the above-cited applications, the device of the presentinvention can be used alone or with other perfuming ingredients,solvents and adjuvants of current use in the art. The nature and varietyof these co-ingredients does not require a detailed description which,moreover could not be exhaustive, and a person skilled in the art willbe able to choose said coingredients by his general knowledge and infunction of the nature of the product to be perfumed and the olfactiveeffect sought. These perfuming ingredients belong to such variedchemical classes as alcohols, aldehydes, ketones, esters, ethers,acetates, nitrites, terpene hydrocarbons, nitrogen- or sulfur-containing heterocyclic compounds, as well as essential oils of naturalor synthetic origin. By way of example, embodiments of compounds can befound in standard reference works, such as the book of S. Arctander,Perfume and Flavor Chemicals, 1969, Montclair, N,J., USA, or more recentversions thereof, or in other works of similar nature.

[0049] The proportions in which the system of the present invention canbe incorporated in the various above-mentioned products vary within awide range of values. These values depend on the nature of the fragrantcompound to be released, the nature of the article or product which isto be perfumed and the desired olfactive effect, as well as on thenature of the co-ingredients in a given composition when the system ofthe present invention is used in admixture with perfumingco-ingredients, solvents or adjuvants of current use in the art.

[0050] By way of example, one can cite typical concentrations of theorder of 0.01 to 5%, or even 10% by weight relative to the weight of theconsumer products cited above into which it is incorporated. Higherconcentrations than those mentioned above can be used when the system isapplied in perfuming compositions, perfumes or colognes.

[0051] The invention will now be described in greater detail in thefollowing examples in which the temperatures are indicated in degreescentigrade and the abbreviations have the usual meaning in the art.

EMBODIMENTS OF THE INVENTION

[0052] General

[0053] The following chemicals were obtained from commercial sources:geraniol, magnesium turnings, 1,2-dichloroethane, 1,2-dibromoethane,2-norbornyl bromide, bromocyclopentane, citronellol, decanol,4-methoxybenzyl alcohol, Lilial®, (-)-menthol, 2-pentylcyclopentanol,4-(1,1-dimethylpropyl)- 1-cyclohexanol, 1-(2-naphthalenyl)ethanol,oxalyl chloride, diethyl oxalate, 3-methyl-2-oxo-pentanoic acid,2-oxopropionic acid, 2-oxobutanoic acid, bromocyclohexane, bromobenzene,2-oxopentanoic acid, 4-bromo acetophenone, ethylene glycol,2-bromo-tetradecane, 1-bromotetradecane.

[0054] Execution of photorelease assays and analysis for α-keto esters

[0055] Photorelease Assays

[0056] Photorelease assays were conducted on solutions or on films ofthe respective ester and will be described below in each of the examplesreferring to the respective mode of irradiation.

[0057] All samples were irradiated using a xenon lamp (Heraeus SuntestCPS at 460W/m2), a UV lamp (UVP Model UVL-28, 8W at 360 nm) or exposedto outdoor sunlight, as will be indicated for each sample in therespective examples.

[0058] Analysis

[0059] The mode of analysis for each sample which had been irradiatedwill be indicated in each respective example.

[0060] Analytical HPLC was carried out on a Spectra Physics instrumentcomposed from a SP 8800 ternary pump, a SP 5750 injection valve, a SP8780 autosampler, a Waters 490E UV detector and a Spectra PhysicsChromJet integratorMacherey-Nagel Nucleosil 5 C₁₈ reversed phase column(125 x 4 mm i.d.) eluted with a gradient from acetonitrile/water 1:1 topure acetonitrile during 20 min. The injection volume was 50 μl and theUV detector wavelength fixed at 220 nm.

[0061] Analytical GC for analysis of all-purpose/window cleanerapplications: the on-column injections were carried out on a Carlo ErbaMFC 500 using a precolumn (30 cm) and a Suppelco SPB-1 capillary column(30 m) at 115° C. for 8 min, then to 280° C., helium pressure 75 kPa,injection volume 2 μl. All other GC analyses were carried out on thesame instrument equiped with a Fisons AS 800 autosampler using a J&WScientific DB1 capillary column (15 m) at 70 or 80° C. for 10 min, thento 260° C., helium pressure 50 kPa, injection volume 0.5 μl.

[0062] Analytical GC for dynamic headspace analysis: Tenax cartridgeswere thermally desorbed in a PE ATD400 or a TDAS 5000 desorber. Thevolatiles were then analysed either with a Carlo Erba HRGC 5300 gaschromatograph coupled to Finnigan ITD-800 mass spectrometers using aSupelco SPB-1 capillary column (60 m, 0.75 mm i.d., film 1 micron) at60° C. for 5 min then to 120° C. (3° C./min) and 280° C. (5° C.citronellal analysis, and at 100° C. then to 250° C. (5° C./min) for thementhone quantification or, alternatively, with a Carlo Erba Vega 6000gas chromatograph using a Supelco SPB-1 capillary column (30 m, 0.53 mmi.d., film 1.5 micron) from 110° C. to 200° C. (6° C./min) using He ascarrier gas in both cases.

EXAMPLE 1

[0063] Preparation of α-keto esters

[0064] The bis(3,7-dimethyl-6-octenyl)oxalate which was used for thesynthesis of some of the α-keto esters described below was prepared asfollows.

[0065] Oxalyl chloride (10 ml, 116 mmol) was added dropwise to a stirredsolution of 36.37 g (233 mmol) of citronellol in 300 ml of pyridine at0° C. over a period of 30 min. The formation of a white precipitate wasobserved. The solution was allowed to warm up at room temperature overnight and was quenched with water, extracted with diethyl ether (2x),H₂SO₄ (10%) (2x), NaHCO₃ (10%) and saturated NaCl. The organic layer wasdried over Na₂SO₄, concentrated at reduced pressure and filtered over ashort plug (SiO₂, heptane/diethyl ether). Column chromatography (SiO₂,heptane/diethyl ether) gave 18.55 g (43%) of a colorless oil.

[0066] IR (neat): 2965s, 2925s, 2873m, 2856m, 1770s, 1745s, 1457m,1380m, 1347w, 1312m, 1250w, 1170s, 1122w, 1044w, 941m, 886w, 831w, 792w,756w, 742w.

[0067]¹H NMR (360 MHz, CDCl₃): 5.13-5.04 (m, I H); 4.40-4.23 (m, 2 H);2.08-1.87 (m, 2 H); 1.85-1.71 (m, 1 H); 1.70-1.50 (m, 2 H); 1.68 (s, 3H); 1.60 (s, 3 H); 1.43-1.29 (m, 1 H); 1.29-1.13 (m, 1 H); 0.94(d,J=6.3, 3 H).

[0068]¹³C NMR (90.6 MHz, CDCl₃): 158.04 (s); 131.45 (s); 124.42 (d);65.59 (t); 36.91 (t); 35.08 (t); 29.42 (d); 25.70 (q); 25.36 (t); 19.36(q); 17.65 (q).

[0069] MS (EI): 336 (M⁺, 0.1); 228 (0.1); 183 (0.1); 165 (0.1); 138(18); 123 (30); 109 (16); 95 (38); 81 (51); 69 (100); 55 (30); 41 (46);29 (5).

[0070] a) 3,7-Dimethyl-6-octenyl-2-oxopropanoate (1)

[0071] A stirred solution of 5.56 g (63 mmol) of 2-oxo propionic acidand 19.68 g (126 mmol) of citronellol in 150 ml of toluene was heatedfor 35 h under reflux with azeotropic removal of water. After cooling toroom temperature the reaction mixture was extracted with diethyl ether(2x), 10% NaHCO₃, sat. NaCl, dried (Na₂SO₄) and concentrated in vacuo.Column chromatography (SiO₂, pentane/ether 9:1) afforded 2.81 g (20%) ofa colorless oil.

[0072] UV/Vis (hexane): 388 (sh, 3); 378 (sh, 5); 369 (sh, 8); 360 (sh,10); 345 (14); 334 (14); 319 (sh, 12); 284 (sh, 9).

[0073] IR (neat): 2961m, 2915m, 2873m, 2856m, 1728s, 1454m, 1378m,1357m, 1297m, 1266m, 1203w, 1134s, 1051m, 1024w, 982m, 937m, 830m, 771w,720m, 663w.

[0074]¹H NMR (360 MHz, CDCl₃): 5.15-5.03 (m, 1 H); 4.37-4.18 (m, 2 H);2.47 (s, 3 H); 2.10-1.88 (m, 2 H); 1.87-1.71 (m, 1 H); 1.71-1.47 (m, 2H); 1.68 (s, 3 H); 1.60 (s, 3 H); 1.46-1.28 (m, 1 H); 1.28-1.12 (m, 1H); 0.94 (d, J=6.3, 3 H).

[0075]¹³C NMR (90.6 MHz, CDCl₃): 191.96 (s); 160.92 (s); 131.52 (s);124.37 (d); 65.06 (t); 36.89 (t); 35.14 (t); 29.39 (d); 26.73 (q); 25.71(q); 25.33 (t); 19.36 (q); 17.66 (q).

[0076] MS (EI): 226 (M⁺, 3); 209 (1); 208 (5); 198 (1), 184 81); 183(9); 165 (2); 156 (1);

[0077] 155 (14); 139 (1); 138 (15); 137 (20); 136 (1); 124 (3); 123(29); 121 (3); 111 (1); 110 (5); 109 (20); 99 (1); 97 (2); 96 (8); 95(45); 94 (2); 93 (1); 91 (1); 90 (1); 84 (1); 83 (15); 82 (28); 81 (51);80 (2); 79 (2); 77 (1); 71 (1); 70 (10); 69 (100); 68 (14); 67 (23); 66(1); 65 (2); 57 (5); 56 (8); 55 (34); 54 (2); 53 (7); 44 (1); 43 (41);42 (5); 41 (40); 40 (2); 39 (6); 29 (4); 27 (3).

[0078] b) 3,7-Dimethyl-6-octenyl-2-oxobutanoate (2)

[0079] The synthesis was carried out as described above under a) with6.43 g (63 mmol) of 2-oxo butyric acid, 19.68 g (126 mmol) ofcitronellol and 150 ml of toluene (24 h). Column chromatography (SiO₂,pentane/ether 9:1) afforded 7.80 g (52%) of a colorless oil.

[0080] UV/Vis (hexane): 397 (sh, 1); 383 (sh, 3); 373 (sh, 6); 356 (sh,12); 341 (16); 330 (16); 318 (sh, 14); 268 (sh, 12).

[0081] IR (neat): 2961m, 2914m, 2879m, 2857m, 1725s, 1456m, 1404w,1379m, 1351w, 1273m, 1242m, 1173w, 1144m, 1097s, 1041m, 982m, 946w,881w, 830m, 760w, 737w, 700m, 678m.

[0082]¹H NMR (360 MHz, CDCl₃): 5.14-5.02 (m, 1 H); 4.40-4.20 (m, 2 H);2.86 (q, J= 7.3, 2 H); 2.09-1.88 (m, 2 H); 1.87-1.68 (m, 1 H); 1.68 (s,3 H); 1.68-1.45 (m, 2 H); 1.60 (s, 3 H); 1.45-1.29 (m, 1 H); 1.29-1.15(m, 1 H); 1.13 (t, J=7.1, 3 H 0.94 (d, J=6.3, 3 H).

[0083]¹³C NMR (90.6 MHz, CDCl₃): 195.09 (s); 161.32 (s); 131.51 (s);124.40 (d); 64.87 (t); 36.90 (t); 35.17 (t); 32.89 (t); 29.40 (d); 25.71(q); 25.34 (t); 19.37 (q); 17.66 (q); 6.97 (q).

[0084] MS (EI): 240 (M⁺, 1); 222 (3); 212 (2); 184 (1); 183 (8); 165(1); 156 (1); 155 (12); 139 (3); 138 (20); 137 (15); 136 (1); 124 (3);123 (31); 121 (3); 111 (2); 110 (4); 109 (16); 104 (2); 99 (1); 97 (3);96 (9); 95 (43); 94 (3); 93 (2); 91 (1); 85 (1); 84 (2); 83 (17); 82(31); 81 (51); 80 (3); 79 (2); 77 (1), 71 (1); 70 (8); 69 (100); 68(13); 67 (19); 66 (1); 65 (2); 58 (2); 57 (63); 56 (7); 55 (30); 54 (2);53 (6); 43 (6); 42 (4); 41 (38); 40 (1); 39 (5); 29 (17); 28 (2); 27(5).

[0085] c) 3,7-Dimethyl-6-octenyl 3-methyl-2-oxopentanoate (3)

[0086] The synthesis was carried out as described above under a), using4.85 g (38 mmol) of 3-methyl-2-oxo pentanoic acid and 11.66 g (74 mmol)of citronellol in 130 ml of toluene, for 72 h. Column chromatography(SiO₂, toluene/EtOAc) afforded 10 g of crude product, which wasfractionally distilled to give 3.65 g (36%) of a colorless oil. B.p. 94°C./2x10¹ Pa.

[0087] UV/Vis (hexane): 394 (sh, 4), 382 (sh, 10), 374 (sh, 10), 365(sh, 10), 350 (sh, 20), 336 (20), 268 (sh, 30), 241 (sh, 180).

[0088] IR (neat): 2966s, 2929s, 2877m, 1749m, 1728s, 1460m, 1380m,1267m, 1254m, 1165m, 1115w, 1087w, 1051m, 1001w, 961w, 829w.

[0089]¹H NMR (360 MHz, CDCl₃): 5.12-5.04 (m, 1 H); 4.36-4.24 (m, 2 H);3.18-3.06 (m, 1 H); 2.08-1.88 (m, 2 H); 1.86-1.67 (m, 2 H); 1.68 (s, 3H); 1.65-1.10 (m, 5 H); 1.60 (s, 3 H); 1.28 (d, J=6.8, 3 H); 0.94 (d, J6.4, 3 H); 0.92 (t, J=7.6, 3 H).

[0090]¹³C NMR (90.6 MHz, CDCl₃): 198.22 (s); 162.21 (s); 131.51 (s);124.40 (d); 64.74 (t); 43.64 (d); 36.92 (t); 35.23 (t); 29.43 (d); 25.71(q); 25.36 (t); 24.93 (t); 19.35 (q); 17.66 (q); 14.55 (q); 11.35 (q).

[0091] MS (EI): 268 (M⁺, 1); 250 (1); 240 (1); 207 (1); 183 (2); 155(2); 138 (10); 123 (14); 109 (7); 95 (18); 85 (32); 81 (26); 69 (51); 57(100); 41 (53); 29 (18).

[0092] d) 3,7-Dimethyl-6-octenyl 2-oxopentanoate (4)

[0093] The synthesis was carried out as described above under a), using4.33 g (37 mmol) of 2-oxo pentanoic acid and 11.65 g (75 mmol) ofcitronellol. Column chromatography (SiO₂, toluene/EtOAc and SiO₂,heptane/diethyl ether) afforded 3.79 g of crude product, which wasdistilled (Kugelrohr) to give 2.52 g (27%) of a colorless oil.

[0094] UV/Vis (hexane): 398 (sh, 1), 376 (sh, 10), 357 (sh, 10), 342(sh, 20), 331 (20), 281 (sh, 20), 268 (sh, 30), 241 (sh, 280).

[0095] IR (neat): 2965s, 2931s, 2877m, 1750m, 1728s, 1457m, 1380m,1287w, 1261m, 1178w, 1146w, 1118m, 1055m, 1037w, 943w, 832w.

[0096]¹H NMR (360 MHz, CDCl₃): 5.13-5.03 (m, 1 H); 4.36-4.21 (m, 2 H);2.80 (t, J=7.31, 2 H); 2.10-1.89 (m, 2 H); 1.83-1.70 (m, 1 H); 1.68 (s,3 H); 1.67 (q, J=7.3, 2 H); 1.63-1.47 (m, 2 H); 1.60 (s, 3 H); 1.45-1.29(m, 1 H); 1.28-1.12 (m, 1 H); 0.96 (t, J=6.9, 3 H); 0.94 (d, J=6.3, 3H).

[0097]¹³C NMR (90.6 MHz, CDCl₃): 194.63 (s); 161.44 (s); 131.52 (s);124.40 (d); 64.88 (t); 41.21 (t); 36.91 (t); 35.19 (t); 29.43 (d); 25.71(q); 25.35 (t); 19.37 (q); 17.67 (q); 16.54 (t); 13.52 (q).

[0098] MS (EI): 254 (M⁺, 1); 236 (2); 226 (1); 193 (1); 183 (6); 165(1); 155 (7); 138 (15); 137 (10); 123 (26); 118 (3); 109 (17); 95 (41);83 (15); 82 (32); 81 (54); 71 (87); 69 (100); 67 (23); 55 (34); 43 (66);41 (72); 27 (14).

[0099] e) 3,7-Dimethyl-6-octenyl oxo(phenyl)acetate (5)

[0100] A Grignard reagent prepared from 3.14 g of 1-bromobenzene (20mmol) and 0.55 g of magnesium (22 mmol) in THF was added dropwise to astirred solution of 8.0 g (22 mmol) ofbis(3,7-dimethyl-6-octenyl)oxalate in 50 ml of THF at -78° C. Themixture was slowly warmed to -10° C., quenched with 25-30 ml of asaturated solution of NH₄Cl and left stirring for 30 min. The reactionmixture was extracted with diethyl ether and water (3x) and the organicphase dried over Na₂SO₄. MPLC on a Lobar column (SiO₂ Merck,heptane/diethyl ether) afforded 3.5 g (61%) of the pure product as abright yellow oil.

[0101] UV/Vis (hexane): 370 (sh, 30), 352 (40), 340 (sh, 40), 294 (sh,1020), 252 (10350), 248 (10360).

[0102] IR (neat): 3065w, 2962s, 2926s, 2872m, 2855m, 1738s, 1693s,1597m, 1581m, 1451m, 1379m, 1322m, 1313m, 1300m, 1246w, 1198s, 1175s,1122w, 1042w, 1030w, 1003m, 998m, 941w, 831w.

[0103]¹H NMR (360 MHz, CDCl₃): 8.04-7.97 (m, 2 H); 7.69.7.62 (m, 1 H);7.55-7.45 (m, 2 H); 5.12-5.03 (m, 1 H); 4.50-4.36 (m, 2 H); 2.15-1.90(m, 2 H); 1.90-1.75 (m, 1 H); 1.75-1.50 (m, 2 H); 1.66 (s, 3 H); 1.59(s, 3 H); 1.45-1.32 (m, 1 H); 1.32-1.15 (m, 1 H); 0.96 (d, J=6.3, 3 H).

[0104]¹³C NMR (90.6 MHz, CDCl₃): 186.50 (s); 164.02 (s); 134.87 (d);132.56 (s); 131.51 (s); 130.02 (d); 128.90 (d); 124.40 (d); 64.85 (t);36.93 (t); 35.30 (t); 29.44 (d); 25.69 (q); 25.38 (t); 19.38 (q); 17.66(q).

[0105] MS (EI): 288 (M⁺, 1); 270 (4); 260 (1); 227 (1); 215 (1); 187(1); 183 (1); 174 (1); 165 (1); 155 (4); 152 (3); 138 (9); 137 (10); 134(2); 123 (11); 109 (8); 106 (10); 105 (100); 96 (3); 95 (20); 83 (3); 82(12); 81 (24); 80 (2); 78 (3); 77 (36); 70 (3); 69 (26); 68 (5); 67(10); 57 (3); 56 (3); 55 (11); 53 (3); 51 (10); 43 (4); 42 (3); 41 (28);39 (5); 29 (4); 27 (4).

[0106] f) 3,7-Dimethyl-6-octenyl (4-acetylphenyl)oxoacetate (6)

[0107] In the first step, 2-(4-bromomethyl)-2-methyl-1,3-dioxolane wasprepared as follows. 10.0 g (50 mmol) of 4-bromo acetophenone, 7.0 g(112 mmol) of ethylene glycol and a few crystals of p-toluene sulphonicacid were dissolved in 100 ml of toluene and heated overnight underreflux with azeotropic removal of water. After cooling to roomtemperature the reaction mixture was concentrated in vacuo. Columnchromatography (SiO₂, heptane/diethyl ether) afforded 11.4 g (93%) of acolorless oil which easily crystallized.

[0108] UV/Vis (hexane): 287 (sh, 400), 274 (sh, 1300), 270 (sh, 1800),259 (sh, 6700), 252 (7800), 227 (sh, 61800), 220 (75600), 217 (sh,75000).

[0109] IR (neat): 3084w, 3060w, 2990m, 2957s, 2928s, 2890s, 2856m,2670w, 1911w, 1691m, 1657w, 1591m, 1575w, 1482m, 1470w, 1443m, 1393m,1373m, 1249m, 1222w, 1196s, 1144m, 1118m, 1092m, 1079m, 1040s, 1010s,947m, 873s, 826s.

[0110]¹H NMR (360 MHz, CDCl₃): 7.49-7.42 (m, 2 H); 7.39-7.32 (m, 2 H);4.08-3.96 (m, 2 H); 3.80-3.69 (m, 2 H); 1.62 (s, 3 H).

[0111]¹³C NMR (90.6 MHz, CDCl₃): 142.49 (s); 131.30 (d); 127.17 (d);121.86 (s); 108.43 (s); 64.47 (t); 27.52 (q).

[0112] MS (EI): 244, 242 (M⁺, 1, 1); 230 (14); 229 (97); 227 (100); 213(5); 211 (5); 186 (4); 185, 183 (51, 53); 171 (2); 169 (2); 157, 155(14, 14); 148 (4); 133 (5); 105 (2); 104 (8); 103 (9); 102 (8); 101 (2);89 (3); 87 (26); 78 (2); 77 (12); 76 (16); 75 (14); 74 (7); 73 (2); 63(4); 62 (2); 51 (7); 50 (13); 43 (41); 39 (3); 29 (7).

[0113] The thus obtained compound was then used as starting product forthe synthesis of 3,7-dimethyl-6-octenyl[4-(2-methyl-1,3-dioxolan-2-yl)phenyl]oxoacetate. The synthesis wascarried out as described above under e), using 4.66 g (20 mmol) of theabove-prepared dioxolane, 0.54 g (22 mmol) of magnesium and 8.0 g (22mmol) of bis(3,7-dimethyl-6-octenyl)oxalate. Column chromatography(SiO₂, heptane/diethyl ether) afforded 4.35 g (58%) of the product as aslightly yellow oil.

[0114] UV/Vis (hexane): 370 (sh, 40), 353 (60), 340 (sh, 60), 296 (sh,1300), 258 (13890).

[0115] IR (neat): 2963s, 2926s, 1736s, 1690s, 1607s, 1573m, 1505w,1455m, 1407m, 1374m, 1347w, 1314m, 1294w, 1250m, 1199s, 1175s, 1146w,1122w, 1100w, 1078m, 1039m, 1018w, 989m, 948w, 890w, 876m, 861m, 833w.

[0116]¹H NMR (360 MHz, CDCl₃): 7.98 (d, J=8.3, 2 H); 7.62 (d, J=8.7, 2H); 5.12-5.04 (m, 1 H); 4.50-4.36 (m, 2 H); 4.13-4.00 (m, 2 H);3.82-3.70 (m, 2 H); 2.10-1.90 (m, 2 H); 1.90-1.75 (m, 1 H); 1.72-1.54(m, 2 H); 1.67 (s, 3 H); 1.65 (s, 3 H); 1.60 (s, 3 H); 1.45-1.32 (m, 1H); 1.30-1.16 (m, 1 H); 0.96 (d, J=6.3, 3 H).

[0117]¹³C NMR (90.6 MHz, CDCl₃): 186.04 (s); 163.97 (s); 150.64 (s);132.12 (s); 131.53 (s); 130.15 (d); 125.97 (d); 124.39 (d); 108.39 (s);64.89 (t); 64.65 (2x) (t); 36.93 (t); 35.30 (t); 29.44 (d); 27.38 (q);25.70 (q); 25.37 (t); 19.38 (q); 17.66 (q).

[0118] MS (EI): 374 (M⁺, 7); 359 (8); 356 (3); 289 (1); 220 (2); 205(1); 192 (32); 191 (100); 176 (2); 160 (2); 155 (2); 148 (24); 138 (16);133 (6); 123 (14); 119 (76); 109 (9); 104 (15); 95 (22); 91 (8); 87(18); 81 (30); 69 (26); 55 (10); 43 (12); 41 (21); 29 (3).

[0119] 3,7-Dimethyl-6-octenyl (4-acetylphenyl)oxoacetate (6)

[0120] 5 ml of H₂SO₄ (50%) were added to a solution of 4.2 g (13 mmol)of the product obtained in the above step in 30 ml of THF. The reactionmixture was heated at 40° C. for 5 h, then extracted with diethyl ether(2x), and saturated solutions of NaHCO₃ (2x) and NaCl (2x). The organiclayer was dried over Na₂SO₄ and concentrated. Column chromatography(SiO₂, heptane/diethyl ether) yielded 2.0 g (47%) of a yellow oil.

[0121] UV/Vis (hexane): 384 (sh, 60), 367 (sh, 100), 343 (sh, 150), 310(sh, 1230), 301 (sh, 1660), 266 (17910), 260 (18440).

[0122] IR (neat): 3051w, 2964s, 2926s, 2872m, 2856m, 1736s, 1693s,1607w, 1570m, 1500m, 1457m, 1434m, 1407m, 1379m, 1359m, 1318m, 1307m,1260s, 1199s, 1176s, 1117w, 1075m, 992s, 959m, 861m, 832m.

[0123]¹H NMR (360 MHz, CDCl₃): 8.17-8.02 (m, 4 H); 5.12-5.04 (m, 1 H);4.53-4.37 (m, 2 H); 2.66 (s, 3 H); 2.14-1.90 (m, 2 H); 1.90-1.75 (m, 1H); 1.73-1.53 (m, 2 H); 1.67 (s, 3 H); 1.60 (s, 3 H); 1.46-1.32 (m, 1H); 1.32-1.12 (m, 1 H); 0.96 (d, J=6.3, 3 H).

[0124]¹³C NMR (90.6 MHz, CDCl₃): 197.19 (s); 185.55 (s); 163.25 (s);141.33 (s); 135.67 (s); 131.57 (s); 130.28 (d); 128.56 (d); 124.34 (d);65.19 (1); 36.91 (t); 35.26 (t); 29.43 (d); 26.94 (q); 25.70 (q); 25.35(t); 19.37 (q); 17.67 (q).

[0125] MS (EI): 330 (M⁺, 4); 312 (1); 302 (1); 281 (1); 269 (1); 194(4); 193 (2); 183 (1); 176 (2); 165 (1); 161 (1); 155 (2); 149 (5); 148(43); 147 (100); 138 (4); 137 (11); 133 (1); 132 (2); 123 (10); 120 (4);119 (11); 110 (2); 109 (10);105 (2); 104 (12); 96 (4); 95 (21); 91 (15);83 (5); 82 (13); 81 (29); 77 (6); 76 (8); 69 ; (38); 698 (5); 67 (11);65 (3); 57 (3); 56 (3); 55 (12); 53 (3); 50 (3); 43 (15); 41 (30); 39(5); 29 (4); 27 (3).

[0126] g) 3,7-Dimethyl-6-octenyl 3-methyl-2-oxopentadecanoate (7)

[0127] The compound was prepared as described above under e), using 5.0g (18 mmol) of 2-bromotetradecane, 0.58 g (24 mmol) of magnesium and7.32 g (20 mmol) of bis(3,7-dimethyl-6-octenyl)oxalate. Columnchromatography (SiO₂, heptane/ diethyl ether) afforded 2.52 g (34%) of acolorless oil.

[0128] UV/Vis (hexane): 394 (sh, 4), 383 (sh, 10), 373 (sh, 10), 365(sh, 20), 349 (sh, 20), 336 (20), 284 (sh, 10), 269 (sh, 20), 241 (sh,140).

[0129] IR (neat): 3440w, 2958s, 2924s, 2854s, 2730w, 1749s, 1725s,1460m, 1378m, 1350w, 1266m, 1173w, 1146w, 1112w, 1053m, 1032m, 943w,887w, 830w.

[0130]¹H NMR (360 MHz, CDCl₃): 5.13-5.04 (m, 1 H); 4.36-4.23 (m, 2 H);3.23-3.10 (m,

[0131]¹H); 2.10-1.87 (m, 2 H); 1.87-1.64 (m, 1 H); 1.68 (s, 3 H);1.64-1.47 (m, 2 H); 1.60 (s, 3 H); 1.46-1.16 (m, 24 H); 1.13 (d, J=6.7,3 H); 0.94 (d, J=6.3, 3 H); 0.88 (t, J=6.9, 3 H).

[0132]¹³C NMR (90.6 MHz, CDCl₃): 198.33 (s); 162.20 (s); 131.50 (s);124.40 (d); 64.75 (t); 42.21 (d); 36.93 (t); 35.23 (t); 31.92 (t); 29.68(t); 29.66 (2x) (t); 29.59 (2x) (t); 29.45 (2x) (t); 29.37 (t); 27.01(t); 25.71 (q); 25.37 (t); 22.70 (t); 19.35 (q); 17.66 (q); 15.01 (q);14.12 (q).

[0133] MS (EI): 408 (M⁺, 1); 390 (1); 380 (1); 347 (1); 294 (1); 272(1); 255 (4); 205 (1); 197 (3); 184 (2); 183 (12); 165 (1); 155 (8); 141(4); 139 (9); 138 (76); 137 (21); 127 (7); 123 (46); 113 (9); 109 (19);99 (15); 96 (15); 95 (57); 94 (8); 85 (47); 83 (25); 82 (52); 81 (89);80 (14); 71 (65); 70 (10); 69 (100); 68 (10); 67 (18); 57 (94); 56 (17);55 (51); 43 (61); 41 (69); 39 (7); 29 (15); 27 (6).

[0134] h) 3,7-Dimethyl-6-octenyl 2-oxohexadecanoate (8)

[0135] The compound was prepared as described above under e), using 5.54g (20 mmol) of 1-bromotetradecane, 0.54 g (22.5 mmol) of magnesium and8.0 g (22 mmol) of bis(3,7-dimethyl-6-octenyl)oxalate. Columnchromatography (SiO₂, heptane/diethyl ether) afforded 3.21 g (39%) of acolorless oil.

[0136] UV/Vis (hexane): 376 (sh, 10), 359 (sh, 20), 343 (sh, 20), 279(260), 272 (sh, 250), 242 (530).

[0137] IR (neat): 2958m, 2924s, 2854s, 1728s, 1465m, 1458m, 1400w,1378m, 1271m, 1128w, 1088w, 1062m, 945w, 831w.

[0138]¹H NMR (360 MHz, CDCl₃): 5.12-5.03 (m, 1 H); 4.35-4.21 (m, 2 H);2.81 (t, J=7.3, 2 H); 2.09-1.88 (m, 2 H); 1.87-1.69 (m, 1 H); 1.68 (s, 3H); 1.69-1.47 (m, 2 H); 1.60 (s, 3 H); 1.45-1.14 (m, 26 H); 0.94 (d,J=6.3, 3 H); 0.88 (t, J=6.9, 3 H).

[0139]¹³C NMR (90.6 MHz, CDCl₃): 194.77 (s); 161.48 (s); 131.49 (s);124.41 (d); 64.86 (t); 39.38 (t); 36.93 (t); 35.20 (t); 31.96 (t); 29.68(3x) (t); 29.61 (t); 29.45 (2x) (t); 29.39 (t); 29.33 (t); 29.01 (t);25.71 (q); 25.37 (t); 23.05 (t); 22.71 (t); 19.38 (q); 17.66 (q); 14.12(q).

[0140] MS (EI): 390 (1), 225 (11), 183 (14), 165 (1), 155 (8), 139 (7),138 (55); 137 (28); 124 (6), 123 (52), 121 (5), 111 (4), 110 (7), 109(27), 97 (9), 96 (16), 95 (70), 94 (8), 85 (16), 83 (28), 82 (50), 81(97), 80 (10), 71 (26), 70 (11), 69 (100), 68 (11), 67 (21), 57 (54), 56(12), 55 (47), 43 (48), 42 (10), 41 (55), 39 (7), 29 (12).

[0141] i) 3,7-Dimethyl-6-octenyl (cyclohexyl)oxoacetate (9)

[0142] The compound was prepared as described above under e), using 3.24g (20 mmol) of freshly distilled 1-bromocyclohexane, 0.55 g (22 mmol) ofmagnesium and 8.0 g (22 mmol) of bis(3,7-dimethyl-6-octenyl)oxalate.MPLC on a Lobar column (SiO₂ Merck, heptane/diethyl ether) finallyafforded 1.69 g (29%) of the pure product as a colorless oil.

[0143] UV/Vis (hexane): 394 (sh, 4), 375 (sh, 11), 366 (sh, 14), 350(sh, 18), 338 (19).

[0144] IR (neat): 2932s, 2856m, 1747m, 1727s, 1451m, 1379m, 1311w,1276m, 1230m, 1183w, 1173w, 1140m, 1118w, 1082m, 1067m, 1050w, 1029w,997m, 942w, 895w, 837w.

[0145]¹H NMR (360 MHz, CDCl₃): 5.12-5.04 (m, 1 H); 4.36-4.22 (m, 2 H);3.07-2.95 (m, 1H); 2.09-1.85 (m, 4 H); 1.85-1.64 (m, 3 H); 1.68 (s, 3H); 1.64-1.47 (m, 2 H); 1.60 (s, 3 H); 1.43-1.13 (m, 8 H); 0.93 (d,J=6.3, 3 H).

[0146]¹³C NMR (90.6 MHz, CDCl₃): 197.65 (s); 162.17 (s); 131.51 (s);124.39 (d); 64.71 (t); 46.34 (d); 36.91 (t); 35.21 (t); 29.44(d); 27.46(t); 25.72 (t); 25.36 (t); 25.30 (t); 19.35 (q); 17.66 (q).

[0147] MS (EI): 294 (M⁺, 1); 276 (1); 266 (1); 233 (1); 193 (1); 183(4); 165 (1); 155 (2); 139 (2); 138 (13); 137 (4); 123 (14); 112 (2);111 (16); 110 (3); 109 (6); 96 (4); 95 (16); 94 (2); 84 (7); 83 (100);82 (15); 81 (22); 80 (3); 70 (2); 69 (29); 68 (4); 67 (11); 56 (4); 55(42); 54 (3); 53 (5); 43 (4); 42 (4); 41 (38); 39 (8); 29 (6); 27 (4),

[0148] k) (E)-3,7-Dimethyl-2,6-octadienyl (cyclohexyl)oxoacetate (10)

[0149] In the first step, ethyl (cyclohexyl)oxoacetate was prepared asfollows. A Grignard reagent prepared from 24.45 g of 1-bromocyclohexane(0.18 mol) and 4.32 g of magnesium (0.15 mol) in 70 ml THF was addeddropwise (during a period of 40 min) to a stirred solution of 14.6 g(0.10 mol) of diethyl oxalate in 150 ml of THF at -70° C. The formationof a precipitate was observed and another 100 ml of THF were added. Themixture was slowly warmed to -10° C. and poured onto ice, saturated withNaCl, extracted with diethyl ether (2x) and washed with a sat. solutionof NH₄Cl (2x) and water (pH˜7). The organic phase was dried over Na₂SO₄and concentrated. Fractional distillation gave 9.86 g (54%) of acolorless oil.

[0150] B.p. 54° C./0.1-1.5 mbar. UV/Vis (hexane): 394 (sh, 5); 375 (sh,10); 366 (sh, 15); 350 (sh, 20); 337 (20); 285 (sh, 7).

[0151] IR (neat): 2982w, 2930m, 2854m, 1722s, 1449m, 1366w, 1272m,1229m, 1184w, 1140m, 1112w, 1081m, 1066s, 1014m, 991m, 923w, 894w, 855w.

[0152]¹H NMR (360 MHz, CDCl₃): 4.32 (q, J=7.1, 2 H); 3.1-2.97 (m, 1 H);1.97-1.85 (m, 2 H); 1.85-1.74 (m, 2 H); 1.74-1.64 (m, 1 H); 1.45-1.13(m, 5 H); 1.37 (t, J=71, 3 H).

[0153]¹³C NMR (90.6 MHz, CDCl₃): 197.65 (s); 162.03 (s); 62.19 (t);46.29 (d); 27.51 (t); 25.73 (t); 25.32 (t); 14.06 (q).

[0154] MS (EI): 184 (M⁺, 2); 112 (3); 111 (33); 110 (3); 84 (6); 83(100); 81 (3); 79 (2); 77 (1); 68 (1); 67 (5); 65 (1); 56 (3); 55 (54);54 (5); 53 (5); 51 (1); 43 (2); 42 (3); 41 (23); 40 (2); 39 (12); 30(1); 29 (20); 28 (3); 27 (13); 26 (1).

[0155] (E)-3,7-Dimethyl-2,6-octadienyl (cyclohexyl)oxoacetate (10)

[0156] A solution of 25.20 g (137 mmol) of the product obtained above,25.56 g (166 mmol) of geraniol and 1 ml of NaOCH₃ (30% in methanol) in150 ml of cyclohexane was heated under reflux overnight. After coolingto room temperature the reaction mixture was taken up in ether, washedwith a sat. solution of NaCl (pH≠7), dried (Na₂SO₄), filtered andconcentrated. Column chromatography (SiO₂, heptane/ether 9:1) andfractional distillation afforded 23.36 g (58%) of a colorless oil.

[0157] B.p. 130° C./0.1 mbar.

[0158] UV/Vis (hexane): 394 (sh, 5); 384 (sh, 8); 375 (sh, 14); 366 (sh,17); 358 (sh, 20); 350 (sh, 22); 336 (24).

[0159] IR (neat): 2926m, 2853m, 1743m, 1721s, 1670w, 1449m, 1376m,1341w, 1331w, 1309w, 1273m, 1267m, 1227m, 1183w, 1139m, 1111w, 1080m,1063s, 1027w, 993s, 915m, 895w, 830w, 805w, 787w, 739w, 729w, 718w.

[0160]¹H NMR (360 MHz, CDCl₃): 5.45-5.35 (m, 1 H); 5.12-5.03 (m, 1 H);4.76 (d, J=7.1, 2 H); 3.09-2.95 (m, 1 H); 2.17-1.98 (m, 4 H); 1.98-1.85(m, 2 H); 1.84-1.75 (m, 2 H); 1.74 (s, 3 H); 1.73-1.62 (m, 1 H); 1.68(s, 3 H); 1.60 (s, 3 H); 1.43-1.14 (m, 5 H).

[0161]¹³C NMR (90.6 MHz, CDCl₃): 197.70 (s); 162.08 (s); 143.97 (s);131.97 (s); 123.59 (d); 117.16 (d); 62.90 (t); 46.38 (d); 39.55 (t);27.49 (t); 26.23 (t); 25.73 (t); 25.67(q); 25.31 (t); 17.69(q);16.58(q).

[0162] MS (EI): 292 (M⁺, 1); 205 (1); 179 (1); 138 (3); 137 (24); 136(4); 135 (3); 123 (1); 122 (1); 121 (2); 112 (1); 111 (9); 107 (2); 105(1); 96 (1); 95 (9); 94 (1); 93 (9); 92 (2); 91 (3); 84 (4); 83 (54); 82(4); 81 (55); 80 (2); 79 (4); 77 (3); 70 (6); 69 (100); 68 (12); 67(12); 65 (1); 56 (1); 55 (24); 54(2); 53 (6); 43 (2); 42 (2); 41 (25);40 (1); 39 (5); 29 (2); 27 (2).

[0163] l) Decyl (cyclohexyl)oxoacetate (11)

[0164] The synthesis was carried out as described above under k), using6.21 g (33.4 mmol) of ethyl (cyclohexyl)oxoacetate, 5.75 g (36.4 mmol)of decanol, 0.5 ml of NaOCH₃ (30% in methanol) and 50 ml of cyclohexane.Fractional distillation afforded 3.85 g (39%) of a colorless oil.

[0165] B.p. 118-126° C./0.2 mbar.

[0166] UV/Vis (hexane): 394 (sh, 4); 382 (sh, 8); 376 (sh, 11); 367 (sh,14); 358 (sh, 17); 350 (sh, 19); 336 (19); 314 (sh, 17); 302 (sh, 15).

[0167] IR (neat): 2924s, 2852m, 1745m, 1723s, 1466m, 1450m, 1377w,1330w, 1310w, 1290w, 1274m, 1229m, 1183w, 1139m, 1117w, 1082m, 1065m,1028w, 995m, 929w, 895w, 867w, 802w, 785w, 720m, 662w.

[0168]¹H NMR (360 MHz, CDCl3): 4.24 (t, J= 6.7, 2 H); 3.07-2.96 (m, 1H); 1.98-1.85 (m, 2 H); 1.85-1.60 (m, 5 H); 1.44-1.14 (m, 19 H); 0.88(t, J=6.9, 3 H).

[0169]¹³C NMR (90.6 MHz, CDCl₃): 197.70 (s); 162.22 (s); 66.27 (t);46.37 (d); 31.90 (t); 29.51 (t); 29.49 (t); 29.30 (t); 29.17 (t); 28.42(t); 27.48 (t); 25.80 (t); 25.74 (t); 25.32 (t); 22.69 (t); 14.11 (q).

[0170] MS (EI): 296 (M⁺, 2); 185 (1); 158 (1); 156 (1); 112 (7); 111(88); 110 (3); 85 (2); 84 (7); 83 (100); 81 (1); 79 (1); 71 82); 70 (1);69 (2); 68 (1); 67 (3); 57 (5); 56 (3); 55 (23); 54 (1); 53 (1); 43 (7);42 (2); 41 (10); 39 (2); 29 (2); 27 (1).

[0171] m) 4-Methoxybenzyl (cyclohexyl)oxoacetate (12)

[0172] The synthesis was carried out as described above under k), using6.62 g (35.9 mmol) of ethyl (cyclohexyl)oxoacetate, 6.06 g (43.9 mmol)of 4-methoxybenzyl alcohol, 0.5 ml of NaOCH₃ (30% in methanol) and 50 mlof cyclohexane. Column chromatography (SiO₂, heptane/ether 7:3) affordedone fraction of the pure product together with another fraction of lowerpurity. The latter was rechromatographed (SiO₂, heptane/ether 8:2) toyield a total of 1.15 g (12%) of pure product as a slightly yellow oil.

[0173] UV/Vis (hexane): 395 (sh, 5); 375 (sh, 15); 367 (sh, 18); 360(sh, 21); 352 (sh, 24); 337 (26); 324 (sh, 25); 312 (sh, 24); 288 (sh,230); 280 (1520); 274 (1790); 268 (sh, 1590); 265 (sh, 1520); 259 (sh,1170).

[0174] IR (neat): 3001w, 2929m, 2853m, 1806w, 1721s, 1612m, 1586m,1514s, 1461m, 1449m, 1424w, 1369w, 1303m, 1271m, 1246s, 1225s, 1174s,1138s, 1112m, 1080m, 1063s, 1031s, 996s, 984s, 946w, 916w, 895m, 849w,821s, 755w, 719w.

[0175]¹H NMR (360 MHz, CDCl₃): 7.38-7.30 (m, 2 H); 6.94-6.85 (m, 2 H);5.21 (s, 2 H); 3.81 (s, 3 H); 3.08-2.94 (m, 1 H); 1.98-1.83 (m, 2 H);1.83-1.71 (m, 2 H); 1.71-1.56 (m, 1 H); 1.41-1.0 (m, 5 H).

[0176]¹³C NMR (90.6 MHz, CDCl₃): 197.39 (s); 161.94 (s); 160.04 (s);130.51 (d); 126.81 (s); 114.08 (d); 67.58 (t); 55.31 (q); 46.41 (d);27.46 (t); 25.70 (t); 25.27 (t).

[0177] MS (EI): 276 (M⁺, 1); 135 (1); 123 (1); 122 (10); 121 (100); 111(2); 107 (1); 106 (2); 94 (1); 92 (1); 91 (3); 90 (1); 89 (1); 83 (7);78 (5); 77 (4); 65 (1); 55 (9); 53 (1); 52 (1); 51 (1); 41 (3); 39 (2).

[0178] n) 3-(4-tert-Butylphenyl)-2-methylpropyl cyclohexyl(oxo)acetate(13)

[0179] The synthesis was carried out as described above under k), using4.8 g (26.1 mmol) of ethyl (cyclohexyl)oxoacetate, 4.0 g (21.5 mmol) of3-(4-tert-butylphenyl)-2-methylpropanol (obtained by reduction of(±)-3-(4-tert-butylphenyl)-2-methylpropanal (Lilial®) with LiAlH₄ inether), 0.5 ml of NaOCH₃ (30% in methanol) and 40 ml of cyclohexane.Column chromatography (SiO₂, heptane/ether 8:2) afforded 3.43 g (46%) ofa colorless oil.

[0180] UV/Vis (hexane): 393 (sh, 4); 384 (sh, 7); 375 (sh, 12); 366 (sh,15); 357 (sh, 18); 351 (sh, 20); 336 (22); 322 (sh, 20); 271 (270); 263(330); 257 (280); 251 (240); 244 (sh, 240).

[0181] IR (neat): 3089w, 3055w, 3021w, 2953m, 2928m, 2855m, 1723s,1512m, 1450m, 1410w, 1387w, 1364w, 1310w, 1270m, 1226m, 1183w, 1139m,1112w, 1079m, 1064m, 998m, 963w, 954w, 919w, 892w, 843w, 800w, 718w,674w.

[0182]¹H NMR (360 MHz, CDCl₃): 7.35-7.27 (m, 2 H); 7.12-7.05 (m, 2 H);4.14 (ABX, J=10.7, 5.6, 1 H); 4.07 (ABX, J=10.7, 6.7, 1 H); 3.06-2.95(m, 1 H); 2.70 (ABX, J=13.7, 6.5, 1 H); 2.48 (ABX, J=13.7, 7.7, 1 H);2.28-2.12 (m, 1 H); 1.97-1.86 (m, 2 H); 1.86-1.74 (m, 2 H); 1.74-1.63(m, 1 H); 1.45-115 (m, 5 H); 1.31 H); 0.98 (d, J=6.7, 3 H).

[0183]¹³C NMR (90.6 MHz, CDCl₃): 197.52 (s); 162.24 (s); 149.01 (s);136.34 (s); 128.75 (d); 125.27 (d); 70.11 (t); 46.44 (d); 39.08 (t);34.43 (d); 34.38 (s); 31.39 (q); 27.44 (t); 25.71 (t); 25.30 (t); 16.77(q).

[0184] MS (EI): 345 ([M+H]⁺, 1); 344 (M^(+, 6)); 330 (1); 329 (6); 234(9); 233 (52); 231 (4); 217 (2); 190 (1); 189 (10); 188 (27); 178 (2);177 (13); 175 (2); 174 (7); 173 (31); 161 (1); 160 (1); 159 (5); 148(6); 147 (45); 146 (1); 145 (8); 133 (3); 132 (23); 131 (29); 130(1);129(2); 128(2); 127(1); 119(4); 118(3); 117(19); 116 (3); 115 (5); 112(3); 111 (40); 110 (1); 105 (5); 104 (2); 103 (1); 91 (9); 84 (7); 83(100); 81 (1); 79 (1); 77 (1); 67 (1); 65 (1); 57 (14); 55 (20); 54 (1);53 (1); 41 (9); 39 (2); 29 (2).

[0185] o) (1R,3R,4S)-3-p-Menthanyl (cyclohexyl)oxoacetate (14)

[0186] The synthesis was carried out as described above under k), using25.03 g (136 mmol) of ethyl (cyclohexyl)oxoacetate, 25.70 g (165 mmol)of (-)-menthol and 1 ml of NaOCH₃ (30% in methanol) in 150 ml ofcyclohexane. Fractional distillation afforded 23.14 g (58%) of acolorless oil.

[0187] B.p. 122° C./0.33 mbar.

[0188] UV/Vis (hexane): 394 (sh, 5); 383 (sh, 8); 375 (sh, 12); 366 (sh,16); 360 (sh, 18); 351 (sh, 20); 337 (22).

[0189] IR (neat): 2949m, 2928m, 2854m, 1717s, 1450m, 1387w, 1370m,1332w, 1311w, 1274m, 1230m, 1181w, 1139m, 1111w, 1081m, 1064m, 1037w,1027w, 1006w, 995s, 980m, 951 m, 912m, 894m, 869w, 844m, 802w, 787w,717m.

[0190]¹H NMR (360 MHz, CDCl₃): 4.83 (td, J=10.9, 4.36, 1 H); 3.05-2.94(m, 1 H); 2.08-1.99 (m, 1 H); 1.96-1.62 (m, 8 H); 1.59-1.45 (m, 2 H);1.44-0.99 (m, 7 H); 0.93 (d, J =6.7, 3 H); 0.90 (d, J=7.1, 3 H); 0.77(d, J=7.1,3 H).

[0191]¹³C NMR (90.6 MHz, CDCl₃): 198.09 (s); 162.16 (s); 76.71 (d);46.79 (d); 46.32 (d); 40.49 (t); 34.10 (t); 31.50 (d); 27.37 (t); 26.25(d); 25.76 (t); 25.32 (t); 25.26 (t); 23.38 (t); 21.95 (q); 20.67 (q);16.17 (q).

[0192] MS (EI): 294 (M⁺, 1); 250 (1); 167 (1); 154 (4); 140 (4); 139(33); 138 (8); 137 (1); 123 (2); 112 (1); 111 (9); 110 (1); 109 (1); 98(1); 97 (16); 96 (1); 95 (5); 84 (7); 83 (100); 82 (2); 81 (12); 80 (1);79 (2); 71 (3); 70 (1); 69 (19); 68 (1); 67 (5); 57 (13); 56 (2); 55(33); 54 (2); 53 (2); 43 (5); 42 (1); 41 (11); 39 (2); 29 (2); 27 (1).

[0193] p) 2-Pentyl-1-cyclopentyl (cyclohexyl)oxoacetate (15)

[0194] The synthesis was carried out as described above under k), using6.62 g (36 mmol) of ethyl (cyclohexyl)oxoacetate, 6.80 g (44 mmol) of2-pentyl cyclopentanol and 1 ml of NaOCH₃ (30% in methanol) in 50 ml ofcyclohexane for 24 h. Column chromatography (SiO₂, heptane/ether 8:2)afforded 5.91 g (55%) of a yellow oil (mixture of diastereoisomers). TheUV/Vis spectrum indicated the presence of a colored impurity.

[0195] UV/Vis (hexane): 395 (sh, 4); 383 (sh, 7); 374 (sh, 11); 366 (sh,14); 358 (sh, 16); 349 (sh, 19); 320 (sh, 23); 303 (sh, 34); 289 (sh,43).

[0196] IR (neat): 2924m, 2853m, 1806w, 1719s, 1461w, 1449m, 1376w,1311w, 1275m, 1254w, 1229m, 1183w, 1139m, 1116w, 1081m, 1064m, 1028w,996m, 968w, 925w, 894w, 844w, 724w.

[0197]¹H NMR (360 MHz, CDCl₃): 5.35-5.28 (m, 1 H); 4.96-4.89 (m, 1 H);3.05-2.88 (m, 2 H); 2.10-1.55 (m, 10 H); 1.53-1.10 (m, 13 H); 0.93-0.80(m, 3 H).

[0198]¹³C NMR (90.6 MHz, CDCl₃): 197.99 (s); 162.29 (s); 162.26 (s);83.72 (d); 80.36 (d); 46.58 (d); 46.42 (d); 45.39 (d); 44.81 (d); 33.49(t); 32.53 (t); 32.07 (t); 31.94 (t); 31.80 (t); 30.20 (t); 29.61 (t);29.12 (t); 28.18 (t); 27.60 (t); 27.46 (t); 27.38 (t); 25.32 (t); 22.76(t); 22.59 (t); 22.03 (t); 14.05 (q).

[0199] MS (EI): 167 (1); 140 (1); 139 (8); 138 (7); 123 (1); 112 (1);111 (11); 110 (1); 109 (1); 98 (2); 97 (25); 96 (2); 95 (3); 84 (7); 83(100); 82 (5); 81 (4); 79 (2); 71 (4); 70 (2); 69 (22); 68 (2); 67 (9);66 (1); 65 (1); 57 (11); 56 (2); 55 (29); 54 (3); 53 (2); 43 (4); 42(1); 41 (12); 39 (3); 29 (3); 27 (1).

[0200] q) 4-(1,1 -Dimethylpropyl)- 1-cyclohexyl (cyclohexyl)oxoacetate(16)

[0201] The synthesis was carried out as described above under k), using6.62 g (36 mmol) of ethyl (cyclohexyl)oxoacetate, 7.40 g (43.5 mmol) of4-(1,1-dimethylpropyl)-1-cyclohexanol and 1 ml of NaOCH₃ (30% inmethanol) in 50 ml of cyclohexane. Column chromatography (SiO₂,heptane/ether 8:2) afforded 4.78 g (43%) of a slightly yellow oil as amixture of cis/trans isomers (˜38:62).

[0202] UV/Vis (hexane): 394 (sh, 4); 385 (sh, 7); 375 (sh, 12); 367 (sh,15); 339 (sh, 35); 326 (40); 312 (sh, 38); 297 (sh, 34); 283 (33); 272(sh, 36).

[0203] IR (neat): 2929s, 2855m, 1800w, 1719s, 1462w, 1448m, 1387w,1377w, 1364w, 1323w, 1309w, 1274m, 1254w, 1228m, 1182w, 1160w, 1140m,1108w, 1081mn, 1064m, 1047w, 1005w, 995s, 948w, 928w, 906w, 894w, 875w,830w, 805w, 780w, 745w, 719w.

[0204]¹H NMR (360 MHz, CDCl₃): 5.21-5.14 (m, 1 H (cis)); 4.85-4.72 (tt,J=11.3, 4.6, 1 H (trans)); 3.07-2.91 (m, 1 H); 2.17-1.04 (m, 21 H);0.83-0.77 (m, 9 H).

[0205]¹³C NMR (90.6 MHz, CDCl₃): 198.07 (s); 161.85 (s); 76.16 (d);72.28 (d); 46.81 (d); 46.35 (d); 44.58 (d); 44.21 (d); 34.82 (s); 34.60(s); 32.75 (t); 32.49 (t); 31.90 (t); 30.49 (t); 27.47 (t); 25.75 (t);25.38 (t); 25.31 (t); 24.97 (t); 24.27 (q); 24.17 (q); 21.22 (t); 8.10(q).

[0206] MS (EI): 264 (1); 193 (1); 181 (1); 153 (4); 152 (3); 137 (4);124 (1); 6); 112 (1); 111 (14); 110 (2); 109 (1); 98 (4); 97 (55); 95(5); 85 (2); 84 (4); 83 (60); 81 (12); 80 (1); 79 (2); 72 (6); 71 (100);69 (13); 68 (1); 67 (11); 57 (15); 56 (3); 55 (51); 54 (4); 53 (3); 43(32); 41 (22); 39 (4); 29 (7); 27 (4).

[0207] r) 1-(2-Naphthalenyl)ethyl (cyclohexyl)oxoacetate (17)

[0208] The synthesis was carried out as described above under k), using6.62 g (24 mmol) of ethyl (cyclohexyl)oxoacetate, 7.5 g (29 mmol) of1-(2-naphthalenyl)ethanol and 1 ml of NaOCH, (30% in methanol) in 70 mlof cyclohexane for 28 h. Column chromatography (SiO₂, heptane/ether 8:2)afforded 2.67 g of a colorless oil still containing about 30% of ethyl(cyclohexyl)oxoacetate.

[0209]¹H NMR (360 MHz, CDCl₃): 7.88-7.78 (m, 4 H); 7.54-7.44 (m, 3 H);6.16 (q, J=6.6, 1 H); 3.08-2.93 (m, 1 H); 1.97-1.60 (m, 5 H); 1.72 (d,J=6.7, 3 H); 1.44-1.12 (m, 5 H).

[0210]¹³C NMR (90.6 MHz, CDCl₃): 197.53 (s); 161.49 (s); 137.73 (s);133.21 (s); 133.13 (s); 128.60 (d); 128.09 (d); 127.71 (d); 126.40 (d);126.34 (d); 125.38 (d); 123.85 (d); 74.76 (d); 46.41 (d); 27.38 (t);25.70 (t); 25.26 (t); 22.08 (q).

[0211] MS (EI): 310 (M⁺, 1); 157 (2); 156 (14); 155 (100); 154 (22); 153(16); 152 (8); 151 (2); 141 (2); 139 (1); 129 (3); 128 (9); 127 (9); 126(2); 115 (4); 111 (3); 101 (1); 84 (1); 83 (17); 77 (4); 76 (4); 75 (2);64 (1); 63 (2); 56 (1); 55 (16); 51 (2); 50 (1); 43 (2); 41 (9); 39 (4);29 (3); 27 (3).

[0212] s) 3,7-Dimethyl-6-octenyl (cyclopentyl)oxoacetate (18)

[0213] In the first step, ethyl (cyclopentyl)oxoacetate was prepared asfollows. A Grignard reagent prepared from 64.0 g of freshly distilledbromocyclopentane (0.43 mol) and 11.0 g of magnesium (0.45 mol) in 360ml of dry ether and filtered under N₂ was added dropwise to a stirredsolution of 48.2 g (0.33 mol) of diethyl oxalate in 300 ml of dry etherat -40° C. The mixture was slowly warmed to 0° C. and poured onto a sat.solution of NH₄Cl, extracted with ether and washed with water (pH˜7).The organic phase was dried over Na₂SO₄ and concentrated. Fractionaldistillation gave 27.1 g (48%) of a colorless oil in sufficient purityfor further derivatization. Column chromatography (SiO₂, heptane/ether8:2) of 2.50 g afforded 2.04 g of product at high purity.

[0214] B.p. 42° C./0.1 mbar.

[0215] UV/Vis (hexane): 389 (sh, 3); 371 (sh, 9); 359 (sh, 13); 345 (sh,15); 336 (15).

[0216] IR (neat): 3483w, 2956m, 2869m, 1723s, 1684m, 1469w, 1449m,1399w, 1372w, 1318w, 1296m, 1254s, 1194m, 1159m, 1140m, 1091s, 1043s,1029s, 952m, 906m, 858m, 780m, 708w.

[0217]¹H NMR (360 MHz, CDCl₃): 4.32 (q, J=7.1, 2 H); 3.56-3.44 (m, 1 H);1.98-1.75 (m, 4 H); 1.75-1.57 (m, 4 H); 1.37 (t,J=7.1, 3 H).

[0218]¹³C NMR (90.6 MHz, CDCl₃): 196.73 (s); 161.98 (s); 62.24 (t);47.42 (d); 28.32 (t); 26.05 (t); 14.05 (q).

[0219] MS (EI): 170 (M⁺, 5); 114 (1); 101 (1); 98 (4); 97 (48); 96 (4);95 (1); 70 (6); 69 (100); 68 (3); 67 (6); 66 (1); 65 (1); 55 (4); 54(1); 53 (2); 51 (1); 43 (1); 42 (2); 41 (22); 40 (2); 39 (7); 29 (5); 28(1); 27 (4).

[0220] 3,7-Dimethyl-6-octenyl (cyclopentyl)oxoacetate (18)

[0221] The synthesis was carried out as described above under k), using6.07 g (35.6 mmol) of the product obtained above, 6.80 g (43.6 mmol) ofcitronellol and 0.5 ml of NaOCH₃ (30% in methanol) in 50 ml ofcyclohexane. Column chromatography (SiO₂, heptane/ether 7:3) afforded5.28 g (53%) of a yellow oil.

[0222] UV/Vis (hexane): 389 (sh, 4); 366 (sh, 12); 345 (sh, 17); 336(17).

[0223] IR (neat): 3493w, 2957m, 2916m, 2869m, 1798w, 1724s, 1687m,1451m, 1377m, 1354w, 1259m, 1190m, 1164m, 1144m, 1091m, 1047m, 1027m,984w, 945m, 829m, 782w, 739w, 717w.

[0224]¹H NMR (360 MHz, CDCl₃): 5.13-5.03 (m, 1 H); 4.40-4.20 (m, 2 H);3.54-3.42 (m, 1 H); 2.10-1.71 (m, 7 H); 1.71-1.45 (m, 6 H); 1.68 (s, 3H); 1.60 (s, 3 H); 1.43-1.30 (m, 1 H); 1.29-1.13 (m, 1 H); 0.94 (d,J=6.3, 3 H).

[0225]¹³C NMR (90.6 MHz, CDCl₃): 196.66 (s); 162.11 (s); 131.51 (s);124.40 (d); 64.75 (t); 47.48 (d); 36.90 (t); 35.22 (t); 29.40 (d); 28.27(t); 26.05 (t); 25.71 (q); 25.35 (t); 19.35 (q); 17.66 (q).

[0226] MS (EI): 280 (M⁺, 1); 262 (2); 252 (1); 184 (1); 183 (6); 165(1); 155 (3); 142 (1); 139 (2); 138 (20); 137 (6); 126 (1); 125 (1); 124(2); 111 (1); 110 (2); 109 (9); 98 (3); 97 (39); 96 (7); 95 (21); 81(23); 80 (2); 79 (1); 70 (7); 69 (100); 68 (5); 67 (9); (10); 54 (1); 53(3); 43 (2); 42 (2); 41 (25); 40 (1); 39 (4); 29 (2); 27 (2).

[0227] t) (E)-3,7-Dimethyl-2,6-octadienyl 3-methyl-2-oxopentanoate (19)

[0228] The synthesis was caried out as described above under a), using4.85 g (38 mmol) of 3-methyl-2-oxo pentanoic acid and 11.5 g (75 mmol)of geraniol in 130 ml of toluene for 24 h. Column chromatography (SiO₂,heptane/EtOAc 95:5) afforded 7.68 g of crude product, which wasfractionally distilled to give 4.04 g (40%) of a colorless oil.

[0229] B.p. 82° C./0.2 mbar.

[0230] UV/Vis (hexane): 393 (sh, 5); 382 (sh, 9); 374 (sh, 13); 364 (sh,17); 357 (sh, 19); 350 (sh, 21); 335 (23).

[0231] IR (neat): 2966m, 2929m, 2878m, 1746m, 1723s, 1670w, 1454m,1377m, 1338w, 1274m, 1244m, 1163m, 1107w, 1085w, 1039s, 999m, 959m,913m, 827w, 796w, 772w, 742w, 705w.

[0232]¹H NMR (360 MHz, CDCl₃): 5.46-5.35 (m, 1 H); 5.14-5.04 (m, 2 H);4.77 (d, J=7.1, 2 H); 3.20-3.07 (m, 1 H); 2.20-2.00 (m, 4 H); 1.83-1.66(m, 1 H); 1.74 (s, 3 H); 1.68 (s, 3 H); 1.60 (s, 3 H); 1.52-1.36 (m, 1H); 1.13 (d, J=7.1, 3 H); 0.92 (t, J=7.5, 3 H).

[0233]¹³C NMR (90.6 MHz, CDCl₃): 198.29 (s); 162.10 (s); 144.01 (s);131.97 (s); 123.58 (d); 117.13 (d); 62.94 (t); 43.66 (d); 39.53 (t);26.22 (t); 25.66 (q); 24.92 (t); 17.69 (q); 16.57 (q); 14.46 (q); 11.35(q).

[0234] MS (EI): 266 (M⁺, 1); 181 (1); 179 (1); 153 (1); 138 (3); 137(28); 136 (6); 135 (5); 123 (1); 122 (1); 121 (2); 109 (1); 107 82); 96(2); 95 (10); 94 (2); 93 (6); 92 (2); 91 (3); 85 (9); 83 (1); 82 (4); 81(52); 80 (2); 79 (3); 78 (1); 77 (3); 71 (1); 70 (6); 69 (100); 68 (12);67 (12); 66 (1); 65 (2); 58 (2); 57 (30); 56 (1); 55 (5); 54 (1); 53(6); 51 (1); 43 (1); 42 (2); 41 (26); 40 (2); 39 (5) 29 (5); 28 (1); 27(2).

[0235] u) 3,7-Dimethyl-6-octenyl (bicyclo[2.2.1]hept-2-yl)oxoacetate(20)

[0236] A Grignard reagent prepared from 4.00 g of 2-norbornyl bromide(23 mmol) and 0.59 g of magnesium (24 mmol) in 30 ml THF was, afterfiltration under N₂, added dropwise (during 45 min) to a stirredsolution of 3.00 g (8 mmol) of bis(3,7-dimethyl-6-octenyl) oxalate in 40ml of THF at -40° C. The mixture was slowly warmed to 0° C., quenchedwith 30 ml of a sat. solution of NH₄Cl. The reaction mixture wasextracted with diethyl ether and water (2x) and the organic phase driedover Na₂SO₄. Repetitive column chromatography (SiO₂, heptane/ether 9:1and heptane/ether 95:5) followed by MPLC on a Lobar column (SiO₂ Merck,heptane/ether 85:15) finally afforded 0.188 g (3%) of the pure productas a colorless oil.

[0237]¹H NMR (360 MHz, CDCl₃): 5.13-5.04 (m, I H); 4.37-4.22 (m, 2 H);3.06 (m, 1 H); 2.59-2.48 (m, 1 H); 2.36-2.27 (m, 1 H); 2.09-1.84 (m, 3H); 1.84-1.69 (m, 1 H); 1.68 (s, 3 H); 1.66-1.45 (m, 4 H); 1.60 (s, 3H); 1.45-1.30 (m, 3 H); 1.30-108 (m, 4H); 0.94(d,J=6.3, 3 H).

[0238]¹³C NMR (90.6 MHz, CDCl₃): 195.33 (s); 162.08 (s); 131.50 (s);124.39 (d); 64.75 (t); 50.37 (d); 39.82 (d); 36.91 (t); 36.28 (d); 35.84(t); 35.23 (t); 31.86 (t); 29.64 (t); 29.43 (d); 28.78 (t); 25.71 (q);25.36 (t); 19.34 (q); 17.66 (q).

[0239] MS (EI): 288 (1); 183 (4); 168 (1); 155 (1); 139 (2); 138 (15);137 (2); 124 (3); 123 (30); 122 (2); 121 (1); 110 (1); 109 (5); 97 (1);96 (11); 95 (100); 93 (4); 91 (1); 83 (4); 82 (19); 81 (21); 80 (5); 79(3); 77 (2); 70 (2); 69 (23); 68 (5); 67 (22); 66 (3); 65 (3); 57 (3);56 (3); 55 (15); 54 (2); 53 (5); 43 (4); 42 (3); 41 (33); 39 (6); 29(5); 28 (1); 27 (5).

EXAMPLE 2

[0240] Release of fragrant aldehydes and ketones from variouscitronellyl α-keto esters in solution or in the neat state

[0241] 0.01 M solutions (5 ml) of the α-keto esters prepared asdescribed in example 1, in toluene, acetonitrile or isopropanol, wereprepared and irradiated with a xenon or a UV lamp or exposed to outdoorsunlight in 10 ml volumetric flasks. Samples in the neat state were alsoirradiated under the same conditions. Before irradiation in solution, 1ml of a 0.01 M solution of decanol was added which served as internalstandard for GC analysis. The results are found in the Table I below.Table I indicates the amount of released aldehyde or ketone in mol%, theamount of remaining starting material is indicated in brackets. It wasalso observed that olefins were released, from compounds (7) and (8) ofexample 1, together with release of citronellal. TABLE 1 Results of thephotoirradiations of different α-keto esters in solution and in theirneat state Yield of Perfume (Remaining Starting Material^(a)) in mol-%Structure of Light Toluene 2-Propanol Acetonitrile Neat Compounds N^(o)Source 3 h 3 h 3 h 3.5 h

 1 Xenon UV sunlight 27 44 (10) (<5) 5 (65) 29 30 (15) (45)

 2 Xenon UV sunlight 33 50 (<5) (<5) 11 (40) 27 29 (5) (15)

 3 Xenon UV sunlight 55 19 23 (<5)^(b)(60) (<5) 5 30 (85) (20) 36 14 15(<5)^(b)(65) (<5) 5 <1 (40) (55)

19 Xenon UV sunlight 15/26^(f)17/21^(f) (<5) (20) 6/26^(f)6/34^(f) (20)(20) 7/12^(f)7/11^(f) (20) (35) 0 (35)

 4 Xenon UV sunlight 38 13 21 (<5)^(b)(75) (<5) 9 13 (45) (20) 31 7 21(10)^(b)(95) (<5) 1 0 (45) (55)

 7 Xenon UV sunlight 11 2/6^(d) (30)^(b)(85) 0/3^(d) (—)^(c) 1/6^(d)(80) 2/11^(d) (30)

 8 Xenon UV sunlight 8 0/5^(e)7/42^(e) (50)^(b)(85) (35) 0/5^(e)3/21^(e)(70) (55) 0/5^(e)0/37^(e) (95) (25) 1/10^(e)0/6^(e) (35) (75)

18 Xenon UV sunlight 24 37 (<5) (<5) 17 (15) 20 22 (5) (15)

20 Xenon UV sunlight 26 (10)

 9 Xenon UV sunlight ≈45 25 38 (<5)^(b)(65) (<5) 9 35 (90) (15) 13 18(70) (<5) 3 <1 (35) (45)^(b)

10 Xenon UV sunlight 26/43^(f)19/25^(f) (<5) (5) 10/33^(f)10/48^(f) (30)(30) 11/19^(f)11/17^(f) (20) (30) <1/0^(f) (50)

11 Xenon UV sunlight 52 52 (0) (<5) 28 26 (5) (5) 27 25 (<5) (<5) 5 4(45) (55)

12 Xenon UV sunlight 81 86 (<5) (<5) 20 (25)^(c) 66 (30)

13 Xenon UV sunlight 69 63 (<5) (<5) 49 (15) 52 53 (<5) (5)

14 Xenon UV sunlight quant. quant. (<5) (10) 53 44 (10) (10) 91 86 (<5)(5) 75 21 (40) (50)

15 Xenon UV sunlight 76 (<5) 53 (15) 75 73 (<5) (10)

16 Xenon UV sunlight 93 93 (<5) (<5) 65 (20) 88 83 (10) (5)

17 Xenon UV sunlight 14 (55)^(e) 6 (90)

 5 Xenon UV sunlight 33 13 27 (10)^(b)(65) (<5) 4 6 (50) (30) 16 7 15(15)^(b)(80) (20) <1 0 (<5) (<5)

 6 Xenon UV sunlight 9 4 (20)^(b)(55) 2 (45) <1 (<5)

EXAMPLE 3

[0242] Release of citronellal from various citronellyl α-keto esters inafter-shave lotions

[0243] Compounds (3) and (4) of example 1 were each dissolved in anamount of 0.29 g in 19.54 g of a standard after-shave lotion base, underaddition of a standard solubilizer (Cremophor RH40, BASF AG). For eachof the compounds, three samples of 6 ml (one of which was wrapped inaluminium foil to serve as reference) were irradiated in 10 mlvolumetric flasks for 3 h with a xenon lamp. The irradiated samples wereanalyzed by HPLC using citronellal and the corresponding startingmaterials as external standards. The reference experiment (aluminiumfoil wrapped) showed no release of citronellal. The results obtainedwith the other samples are summarized in Table 2. TABLE 2 Results of thephotoirradiations of α-keto esters in after-shave lotion mol-% ofcitronellal mol-% of remaining * Compound N^(o) iberated startingmaterial 3 12 36 4  2 53

EXAMPLE 4

[0244] Release of citronellal or menthone from various citronellylα-keto esters in a window cleaner and in an all-purpose cleaner

[0245] 10-15 mg of the respective α-keto ester as specified in Table 3below were weighed into 10 ml volumetric flasks. A solubilizer was added(Cremophor RH40, BASF AG for window cleaner, Triton X100 (Rohm & Haas)for all-purpose cleaner), before adding 6 ml of the respective base,i.e. a standard type window cleaner, or a Fabuloso® (registeredtrademark of Colgate-Palmolive, USA) type all-purpose cleaner, andagitating until the solution became clear. For each irradiation seriesfour samples were prepared for each compound, one of which, wrapped inaluminium foil, served as reference. All the samples were irradiated for3, 6, or 15 h with either the Xenon or the UV lamp or exposed to outdoorsunlight. In all cases the formation of citronellal or menthone could besmelled after the photolysis. In order to quantify the amount ofaldehyde or ketone (and of the remaining starting material) in theapplication base, the irradiated samples were subjected to GC analysis(extraction and on-column injection).

[0246] For analysis, 1 g of NaCl was added and the samples wereextracted with 3 ml of a 0.35 mM (50 mg/l) solution of undecane (used asinternal standard) in iso-octane. The aqueous layer was re-extractedwith 2 ml of the iso-octane solution and the two organic phases werecombined and injected directly onto a GC column. The results obtainedfor the different bases are summarized in Table 3. TABLE 3 Results ofthe photoirradiations of different α-keto esters in different householdapplication bases Yield of Remaining Structures of Tested LightIrradiation Perfume^(a) Starting Material Compounds N^(o) ApplicationSource Time in mol-% in mol-%

 3 Window Cleaner (solution) Xenon   UV     Sun 3 h 6 h 3 h 6 h 15 h 3 h6h 8 3 2 3 6 3 2 (50) (10) (90) (70) (60) (90) (40) Fabuloso ®(solution) Xenon   UV   Sun 3 h 6 h 3 h 15 h 3 h 6h 6 2 3 10 <1 <1 (25)(5) (85) (45) (60) (30)

 9 Window Cleaner (solution) Xenon   UV     Sun 3 h 6 h 3 h 6 h 15 h 3 h3 6 3 3 6 8 (15) (20) (80) (70) (35) (75) Fabuloso ® (solution) Xenon  UV   Sun 3 h 6 h 3 h 15 h 3 h 1 <1 1 15 <1 (25) (10) (85) (45) (50)

 5 Window Cleaner (solution) UV 3 h 1 (40)

14 Window Cleaner (solution) Xenon   Sun 3 h 6 h 3 h 6 h 26 22 28 37(40) (25) (80) (75) Fabuloso ® (solution) Xenon   Sun 3 h 6 h 3 h 6 h 3715 36 32 (35) (20) (80) (50)

EXAMPLE 5

[0247] Dynamic headspace analysis in all purpose cleaners (APC)

[0248] In order to follow the perfume release under more realisticapplication conditions, quantitative dynamic headspace analyses werecarried out. The formation of citronellal from its precursor in an APCapplication was compared to the behaviour of free citronellal in thesame base. Solutions of a base of the Fabuloso® type containing either0.3 mass-% of citronellal precursor 9 or 0.3 mass-% of pure citronellal(˜2 molar equivalents) were prepared and deposed in self-built 3.5 1Pyrex® glass containers covered with a thin window glass plate. Thechambers were exposed to outdoor sunlight for 6 h and continuouslyflushed with an air stream. Every hour the volatiles contained in theair stream were adsorbed on a Tenax cartridge (during 15 min) and thelight intensity was measured. The amount of citronellal trapped on thecartridges was desorbed and quantified by GC analysis and are summarizedin Table 4.

[0249] The amount of citronellal released increases with increasinglight intensity and decreases when the intensity decreases, with themaximum of release being obtained shortly after the maximum ofirradiation was measured. The amount of free citronellal, however, wasfound to decrease steadily with increasing time and, no dependency onthe light intensity was observed. TABLE 4 Comparison of the dynamicheadspace of free citronellal and citronellal released from precursor ina Fabuloso ® type APC irradiated with outdoor sunlight. Free citronellalin base Citronellal released from Sunlight Time (0.3 mass-%) precursor 9in base intensity [h] [ng 1⁻¹] (0.3 mass-%) [ng 1⁻¹] [lux] 1 154086 1579 38500 2 117735  4752 53500 3 67015 7475 64500 4 50632 7829 63000 533215 7297 52500 6 19757 5919 35000

[0250] The above described experiment was repeated using 0.3 mass-% ofmenthone precursor 14 or 0.15 mass-% of pure menthone (˜1 molarequivalent) in an APC application of the Fabuloso® type. Again adependency of perfume release of the irradiation intensity could beobserved, see Table 5, whereas the amount of unprotected menthonedecreased continuously over time. Working with molar equivalents insteadof mass equivalents shows that the perfume concentration of both systemsare in the same order of magnitude. At the beginning of the experimentthe concentration of unprotected menthone is about three times strongerthan the concentration of the perfume released from the precursor. Atthe end of the experiment the perfume released from the keto estercontributes more strongly than the free menthone. TABLE 5 Comparison ofthe dynamic headspace of free menthone and menthone released fromprecursor 14 in a Fabuloso ® type APC irradiated with outdoor sunlightFree menthone in base Menthone released from Sunlight Time (0.15 mass-%)precursor 14 in base intensity [h] [μg 1⁻¹] (0.3 mass-%) [μg 1⁻¹] [lux]0.5 94.6 33.1 53000 1.5 86.4 59.7 71000 2.5 81.5 70.0 86750 3.5 76.768.9 88500 4.5 64.2 63.3 80500 5.5 47.4 60.5 69250 6.5 39.1 48.1 53000

EXAMPLE 6

[0251] Dynamic headspace analysis for the slow release on hair

[0252] In order to test the performance of the controlled photochemicalrelease of perfumes in typical body care applications, 0.2 mass-% ofprecursor 9 dissolved in a leave-in hair conditioner of the standardtype was sprayed four times on a hair curl (˜5 g weight) and irradiatedin a glass tube for 3 h with a Xenon lamp. The hair curl had been washedbeforehand with an unperfumed shampoo base and the amount of conditionerdeposed on the hair was weighed precisely. A comparison experiment with0.1 mass-% (˜ 1 molar equivalent) of unprotected citronellal in the samebase was carried out under identical conditions.

[0253] During irradiation, the glass tube was connected to a charcoalfilter (for air decontamination) and a Tenax cartridge and continuouslyflushed with an air stream (80 ml/min, corresponding to 4 renewals ofair/sampling). The diffusion of citronellal was monitored over a periodof three hours and four samplings at t=0, 1, 2 and 3 h were carried out.At each sampling, the citronellal diffusing from the hair was adsorbedonto a Tenax cartridge during 15 min, respectively. The cartridges werethen thermally desorbed and the concentration of citronellal preciselyquantified by GC (Table 6). TABLE 6 Comparison of the dynamic headspaceof free citronellal and citronellal released from precursor 9 in aleave-in hair conditioner irradiated with a Xenon lamp. Free citronellalin Citronellal released from Xenon light Time hair conditioner (0.1precursor 9 in hair conditioner intensity [h] mass-%) [ng 1⁻¹] (0.2mass-%) [ng 1⁻¹] [lux] 0 20700  284 78000 1 435 394 86000 2 127 23786500 3  39 151 87500

[0254] Table 6 illustrates that the concentration of unprotectedcitronellal decreases rapidly with time whereas the citronellal releasedfrom the precursor remains almost constant during the experiment withconstant light intensity. After only one hour of irradiation theconcentration of citronellal released from the precursor is as high asthe concentration of the unprotected aldehyde, and thereafter remainshigher than the concentration of the unprotected aldehyde.

EXAMPLE 7

[0255] Dynamic headspace analysis for the slow release on cotton fabric

[0256] The release of citronellal from precursor 9 was compared to thediffusion of unprotected aldehyde on cotton fabric. For the study,precisely determined amounts of ethanolic solutions containing either0.2 mass-% of 9 or 0.1 mass-% (˜1 molar equivalent) of unprotectedcitronellal, respectively, were sprayed four times on 4 x 20 cm cottonsheets, which had been washed beforehand with an unperfumed detergentbase. The irradiation was carried out in a Pyrex® glass tube for 3 hwith a Xenon lamp as described above.

[0257] Again a rapid decrease of the released amount unprotectedcitronellal over time was observed, whereas the release of citronellalfrom the precursor remained constant with respect to the irradiationintensity, as illustrated in Table 7. The light dependence of thecontrolled perfume release was verified in a blank experiment. Afteronly 3 h of irradiation comparable concentrations of citronellal wereobtained either from the experiment with the free perfume or fromrelease of the precursor compound. TABLE 7 Comparison of the dynamicheadspace of free citronellal and citronellal released from precursor 9on cotton sheets irradiated with a Xenon lamp. Free citronellalCitronellal released on cotton (0.1 mass- from precursor 9 Xenon lightTime % in EtOH) on cotton (0.2 mass- intensity [h] [ng 1⁻¹] % in EtOH)[ng 1⁻¹] [lux] 0-0.25 3022 71 92500 1-1.25 1590 168 89250 2-2.25  469150 80750 3-3.25  116 115 81750

EXAMPLE 8

[0258] Slow release from cotton sheets treated with fabric softener

[0259] In a typical experiment, ten cotton towels were washed with anunperfumed, lipase free detergent powder and a fabric softenercontaining either 0.8 mass-% of keto ester 9 or 0.23 equivalents of thetheoretically releasable unprotected aldehyde, respectively. The towelswere washed at 40° C. without prewashing cycle and dried in the darkovernight. Two towels of each type were irradiated with the abovedescribed UV lamp in one covered Pyrex® crystallizing dish with anapproximative volume of 3.5 l and compared to a set of non irradiatedsamples. After 3 h of irradiation the towels were analyzed by ninepanelists. In all cases the irradiated towels with precursor 9 werecharacterized to give a fresh, floral, citrus type odor, and the averageintensity was given the value 3 on an increasing scale starting at 0 andending at 10. In the case of the unprotected citronellal or the twoblank samples, the panelists detected only a weak odor with an intensityof 1 on the scale from 0 to 10.

[0260] The photoperfume precursor can therefore sucessfully be deposedon fabrics in a normal washing cycle, and the release of the desiredperfume is detected in perceptible amounts upon irradiation of the dryfabric.

EXAMPLE 9

[0261] Release of menthone from an all-purpose cleaner

[0262] An all-purpose cleaner of the Fabuloso® type containing 0.3% ofthe compound 14 was prepared. This cleaner and the same cleaner withoutany perfume were placed into trapezoid flashes which were exposed tosunlight for 3 h (see also Example 4). The thus-obtained samples werethen compared on a blind test by a panel of 15 non-experts. When thesample containing the photoperfume was the odd sample, 14 of thepanelists correctly distinguished the samples. When the odd sample wasthe one containing the unperfumed base, 13 of the panelists correctlyattributed the samples.

EXAMPLE 10

[0263] Release of menthone from a window cleaner

[0264] A window cleaner of the type described in Example 11 containing0.3% of the compound 14 was prepared. This cleaner and the same cleanerwithout any perfume were placed into trapezoid flashes which wereexposed to sunlight for 3 h. The thus-obtained samples were thencompared on a blind test by a panel of 15 non-experts. When the samplecontaining the photoperfume was the odd sample, 12 of the panelistscorrectly distinguished the samples. When the odd sample was the onecontaining the unperfumed base, 10 of the panelists correctly attributedthe samples.

1. A system for the delivery, upon irradiation, of a fragrant aldehydeor ketone derived from a primary or secondary alcohol R″*OH or of afragrant compound containing an olefin function and derived from theorganic group R′*, or both, said system comprising an α-keto ester offormula

in which R′* is hydrogen or a linear or branched, unsubstituted orsubstituted alkyl group or alkylene group from C₁ to C₃₅, anunsubstituted or substituted cycloalkyl group from C₃ to C₈, anunsubstituted or substituted phenyl group, wherein said alkyl, alkylene,cycloalkyl and phenyl groups may comprise one or several hetero atomsnot directly linked to the α-keto group and selected from the groupconsisting of oxygen, nitrogen, phosphorous and sulfur, or R′* is asubstituted or unsubstituted, linear or branched alkyl group carrying anabstractable hydrogen in γ-position relative to the α-keto function andcomprising a moiety from which is derived a fragrant compound containingan olefin function, such that said fragrant compound containing anolefin function is eliminated after abstraction of said γ-hydrogen atom;R″* is hydrogen or a methyl, ethyl or tert-butyl group or is the organicpart of a primary or secondary alcohol R″OH from which is derived afragrant aldehyde or ketone, and wherein at least one of the groups R′*and R″* is a group derived from a fragrant compound:
 2. The systemaccording to claim 1 wherein R″* is the organic part of a primary orsecondary alcohol from which is derived a fragrant aldehyde or ketoneand wherein R′* is a substituted or unsubstituted phenyl group, acyclohexyl group, a cyclopentyl group, or a linear or branched alkylgroup from C₁ to C₄, with the exception of a n-butyl group.
 3. Thesystem according to claim 1 , wherein R′* is a phenyl group, acyclohexyl group, a cyclopentyl group, a methyl group, an ethyl group,or an isopropyl group.
 4. The system according to claim 1 , wherein thefragrant aldehyde or ketone from which is derived the primary orsecondary alcohol from which the organic part R″* is present in thea-keto ester as defined in formula (I) is citronellal, citral,hydroxycitronellal, methyl dihydrojasmonate,4-(4-hydroxy-1-phenyl)-2-butanone,[3-(4-tert-butylphenyl)-2-methylpropanal], ortho- or para-anisaldehyde,menthone, 2-pentyl- 1-cyclopentanone, 2-naphthalenyl- 1-ethanone, 4-(1,1-dimethylpropyl)-1-cyclohexanone, benzyl acetone, or a saturated,unsaturated, linear or branched aldehyde from C₆ to C₁₃.
 5. The systemaccording to claim 1 , wherein the fragrant compound containing anolefin function from which is derived R′* in formula (I) is linalool,myrcene, myrcenol, a 1,3,5-undecatriene, 9-decen-1-ol, or allylheptanoate.
 6. A method to improve, enhance or modify the odoriferousproperties of a perfuming composition or a perfumed article, whichmethod comprises adding to said composition or article an effectiveamount of an α-keto ester as described in claim 1 , provided that decyl2-oxopropanoate, (Z)-3-hexenyl 2-oxopropanoate and 2-ethyl-3-methylbutyl2-oxopropanoate are excluded.
 7. Perfuming composition or perfumedarticle, containing the delivery system according to claim 1 . 8.Perfuming composition or perfumed article according to claim 7 in theform of a perfume or a cologne, a bath or shower gel, a hair-careproduct, a cosmetic preparation, a body deodorant, a solid or liquidair-freshener, a detergent or a fabric softener, or a household product.9. Perfumed article according to claim 8 , in the form of an all purposecleaner or an all purpose household cleaner, a window cleaner, afurniture polish, a fabric conditioner, softener or wash in form of apowder, a liquid or a tablet, a shampoo, a hair conditioner, a leave-inhair conditioner, or a hairspray.
 10. An α-keto ester of formula

in which R′* is a linear or branched, unsubstituted or substituted alkylgroup or alkylene group from C₁ to C₃₅, an unsubstituted or substitutedcycloalkyl group from C₃ to C₈, a substituted phenyl group, wherein saidalkyl, alkylene, cycloalkyl and phenyl groups may comprise one orseveral hetero atoms not directly linked to the α-keto group andselected from the group consisting of oxygen, nitrogen, phosphorous andsulfur, or R′* is a substituted or unsubstituted, linear or branchedalkyl group carrying an abstractable hydrogen in γ-position relative tothe α-keto function and comprising a moiety from which is derived afragrant compound containing an olefin function, such that said fragrantcompound containing an olefin function is eliminated after abstractionof said γ-hydrogen atom; R″* is hydrogen or a methyl, ethyl ortert-butyl group or is the organic part of a primary or secondaryalcohol from which is derived a fragrant aldehyde or ketone, and whereinat least one of the groups R′* and R″* is a group derived from afragrant compound; provided that R′* is not a methyl group, R″* is not amenthyl or a benzyl group, and that (-)-(1S, 1R) 1,7,7-trimethylbicyclo[2.2.1 ]heptan-2-yl (4-methylphenyl)oxoacetate andhexyl (cyclohexyl)oxoacetate are excluded.
 11. An α-keto ester accordingto claim 10 wherein R″* is the organic part of a primary or secondaryalcohol from which is derived a fragrant aldehyde or ketone and in whichR′* is a cyclohexyl group, a cyclopentyl group, or a linear or branchedalkyl group from C₁ to C₄, with the exception of a n-butyl group.
 12. Anα-keto ester according to claim 10 , wherein the alkyl group is amethyl, ethyl or isopropyl group.
 13. An α-keto ester according to claim10 , wherein the fragrant aldehyde or ketone from which is derived theprimary or secondary alcohol from which the organic part R″* is presentin the α-keto ester as defined in formula (I) is citronellal, citral,hydroxycitronellal, methyl dihydrojasmonate,4-(4-hydroxy-1-phenyl)-2-butanone,[3-(4-tert-butylphenyl)-2-methylpropanal], ortho- or para-anisaldehyde,menthone, 2-pentyl-1-cyclopentanone, 2-naphthalenyl- 1-ethanone,4-(1,1-dimethyl)-1-cyclohexanone, benzyl acetone or a saturated,unsaturated, linear or branched aldehyde from C₆ to C₁₃.
 14. An α-ketoester according to claim 10 , wherein the fragrant compound containingan olefin function from which is derived R′* in formula (I) is linalool,myrcene, myrcenol, a 1,3,5-undecatriene, 9-decen-1-ol, or allylheptanoate.